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Offline map with less zoom size and maximum area covered

Offline map with less zoom size and maximum area covered


I am developing a mobile app for which an offline map is required. Is it possible to have such map within few 10s of MBs? The requirement is to have:

  1. Map with smaller zoom size; e.g. In this URL of Google Maps, the z denotes the zoom size (following longitude, latitude): https://www.google.co.in/maps/@12.9677753,77.6490654,15z; Hence 15 Google Map equivalent zoom size is manageable, I am ok with 14 as well if it reduces the size considerably
  2. The map can be a big image file with names of the street etc. printed
  3. The map should cover at least a country as big as US/Canada (if not the whole world)

Google maps doesn't seem to help. I also tried OpenStreetMap and its various links but what I found was the map size of 30-40 GB. I referred following question as well, but unable to get answer:
Offline Map Service with Mapnik and Leaflet

From where can I download such small size map or what is the minimal size of map which has bare minimal street view (not sure if this link can help)?


There is no way you can get the map that small and still be readable like at that zoomlevel.

Just consider this:

  • the scalebar on gmaps (bottom right corner) is roughly 1", so even at z14: 1 km = 1 inch
  • an imaginary country with 1000km*1000km, so a map of that country would take 1000"x1000" (1000000)
  • you want it colored, so at least 8bit, i.e. *8
  • you want to identify objects within that 1km (=1"), so you can't use 1dpi… let's take 50dpi, so *50

now we are at 1000000 * 8 * 50 =~ 50MB

what do we get for our 50MB?

  • 256 colors (might be enough for a street-map)
  • 50dpi, which isn't close to readable
  • a 1000*1000km country (as comparison: canada is ~5500km*4500km)

I've done extensive research on this topic, because my current project demands offline-mapping functionality.

I'll save you a lot of time by pointing you at some of the available open-source tools & projects I've found.

This project is no longer maintained. However, it reads directly from osm.pbf files and renders the maps successfully. You will have to manage the size of the region you want to map, because this implementation seems to hang and eventually crash if you try to load an entire country into it. I used a 25mb osm.pbf file for a subset of the LA region and it worked great. I think the rendering engine needs optimization.

This one is faster and seems to do a better job rendering the vector data.

This is an open-source C++ library for offline rendering and routing with vector maps. It is actively maintained (see their mailing list). I had trouble getting it to compile on Mac OSX but maybe you will have better luck. Seems to be a very capable, powerful, and portable library. They've gotten it running on Fedora, Moblin, Ubuntu, Debian, Windows, Qt, and Mac OSX/iOS.

Good luck. If you achieve some kind of breakthrough using these tools, please come back and share your results. I'm working on the same stuff and I could use pointers myself.


Tilesets

Tilesets are lightweight collections of map data that are optimized for rendering and are not editable but can be styled in the Mapbox Studio style editor.

What are tilesets used for?

Consider uploading your data as a tileset if your data is large and doesn't need to be updated often.

If you created a vector tileset by uploading geospatial data that contains attributes, the resulting vector tileset will inherit the attributes contained in your raw data source. Here are a few examples of what you can do with the attributes belonging to features in a vector tileset:

  • Use Mapbox Studio to customize the color of a state based on its population density.
  • Use the Mapbox Maps SDK for iOS to dynamically style trees based on an AGE attribute.
  • Use Mapbox GL JS to highlight counties share a similar name.

How tilesets work

When you upload data as a tileset or export a dataset as a tileset, Mapbox breaks it up into a uniform grid of square tiles at preset zoom levels. It must undergo many processing steps to load quickly and be lightweight.

When you use either the Uploads API or Mapbox Studio (which uses the Uploads API behind the scenes) to turn data into a tileset, two things happen:

  1. Simplification: The Mapbox Uploads API analyzes your data for complexity and automatically removes unnecessary vertices at variable rates depending on zoom level. This process is called simplification, and it helps make sure your maps load quickly, especially at lower zoom levels where additional complexity would not be visible.
  2. Determining the zoom extent. The Mapbox Uploads API keeps your tilesets light by examining your data's extent (the geographic area covered by your data) and complexity and only creates vector tiles for zoom levels that are likely to be required — a zoom extent is defined. For datasets with small zoom extents or complex features, this usually means low zoom levels (zoomed out) will be discarded. For large features that are not complex, this usually means higher zoom levels (zoomed in) will be discarded. If you need your tileset to be visible at a different zoom extent, you can adjust this manually, but it is important to note the following:
  • Minimum zoom levels can be increased, but not decreased past the assigned minimum zoom level.
  • Maximum zoom levels can be decreased and increased, since data can be overzoomed and visualized to zoom 22.

If you use Mapbox Tiling Service to turn data into a tileset, you will set the simplification level and the zoom extent in the tileset recipe.

You can create tilesets by uploading data in any of the following formats:

FormatUpload limit
CSV1 GB transfer limit ( 300 MB if uploaded with Studio)
GeoJSON1 GB transfer limit ( 300 MB if uploaded with Studio)
MBTiles25 GB transfer limit ( 300 MB if uploaded with Studio)
KML260 MB with 15 or fewer layers
GPX260 MB
Shapefile260 MB (combined uncompressed size of .shp and .dbf files). You must upload Shapefiles as a compressed (.zip) file.
GeoTIFF10 GB

Raster and vector tilesets

Tilesets can be created with raster or vector data.

If you upload raster data (such as a GeoTIFF), the resulting raster tilesets will only contain raster data, a pixel-based data format that all digital photographs conform to.

If you upload vector data, this will create a vector tileset containing vector data, which consists of mathematically calculated points, lines, and polygons as coordinate pairs. Mapbox GL takes advantage of vector tilesets by calculating and rendering vector data directly in your browser.


GIS Interactive Mapping

These Interactive Mapping Services allow the user to view, query and print GIS information for any extent of the town. Each mapping service provides the user with a unique set of functions that were specifically tailored for common everyday use within the town. Through the use of these services, the user can produce high quality GIS maps for their use as well as perform spatial operations, such as buffer notifications, with the click of a mouse right from their home computer.

  • Aerial Imagery Updated: April, 2020
  • Assessment Data Current To: May, 2021. Regularly scheduled daily updates of CAMA data are currently paused while the site undergoes maintenance.
  • Parcel Data Current To: 10/1/2020
    Parcel Map Data is Current to the Grand List of the Shown Year. Subsequent edits have been made since the close of the Grand List however they may not be complete and current to today's date.

For additional assistance, please contact the IT Help Desk

GIS Viewer
This application can be viewed in any web browser and used on any smartphone or tablet. Users are able to access Assessment information, Deeds, Property Cards, and pictures. Several map themes are available to overlay including: Utility Data, Parcel Annotation, Districts, such as Fire and Zoning, and Environmental Data. Users can also toggle between several years&rsquo worth of orthophotography.
The values shown are based on the findings during the 2016 Town Wide Revaluation, and the land & building characteristics are based on the findings for the 2020 Grand List

FEMA Flood Maps
FEMA flood maps are flood hazard information produced by the National Flood Insurance Program (NFIP). FEMA mapping identifies flood hazards and evaluates flood risk areas. FEMA has partnered with states and communities to provide accurate flood hazard and risk data to guide them to mitigation actions.

Voting District Map
This application is designed to help users find a voting location within the town. Click a location directly on the map to find a voting location or search for the address of your polling place in the search bar. When a polling location is within the polygon layer, you will see information about the polling location and the related district boundary will be highlighted on the map.

Groton Image Compare
Ever wanted to see changes in Groton right before your eyes? With Image Compare you can view two images from different years side by side in the same extent. Imagery ranges from 1990 to 2015. Use the "Bookmark Tool" to zoom to and view areas we've picked out for you to see change.

Groton Coastal Accessibility
This application allows users to view locations where the public can access Groton's coastline on their PC, tablets or smartphone. Just clicking on one of the coastal locations, and the map will then zoom to its location. Display an informational window showing basin information, by click on coastal area in the map. View photos from the area, by clicking on the camera or information logo on the map.

Park Viewer
This application helps citizens locate a park and obtain information about recreation activities in their community. Searches can be conducted by park name or amenity within the park. This application is typically used to locate a park or recreation area near them, or one that offers the activity they are interested in.

Guide to Hiking Trails
Want to go on a hike? This web application allows users to view trails on their PC, tablets or smartphone. This web page includes trail facts, downloadable trail maps, create your own trail map, and find my location when you out on a trail. The trail systems include Town of Groton trails, State owned trails, and private Open Space trails. These trails are owned and managed by Groton Open Space Association (GOSA) and the Avalonia Land Conservancy.

New London County ParkRx
New London County Parks and Recreation Departments have come together to create the New London County Park Prescription program. This program has partnered with public land agencies, and healthcare providers to encourage people to utilize parks, trails, and open space for the purpose of improving individual and community health. You can search for the closes park near you by typing in an address in the search bar or click a location button then directly on the map. A list of amenities in your area will then appear.


12 Answers 12

Note: many of these applications use map data from a really cool free map project called OSM (OpenStreetMap), which anyone can contribute to. OSM is constantly improving, but in many areas it may lack information like house/building numbers.

    • Google Maps does have some offline functionality (including offline navigation as of version 9.17), but the size of the area you can download is limited (you can't download an entire US state, for instance) and some countries or areas aren't available for download. See here for instructions: Download a map and use it offline
    • Unless you're looking to support OSM, this is probably the best free option out there. It works offline, has maps in nearly 200 countries, and turn-by-turn navigation in over 100 countries. Features include full street addresses, points of interest, alternate routes, traffic, public transport, and speed limits. Notable features that are missing: ability to add multiple stops to a route, lane assist, rerouting based on traffic, and ability to navigate to contacts' addresses.
    • Open-source, uses data from OSM. Currently only has 2D navigation, but one of the better free options available.
    • OSM-based offline navigation. Fairly basic but promising. TomTom maps available as an in-app purchase.
    • Ad-supported. Allows you to download maps for offline navigation, also OSM-based. OSM has maps for the whole world, but for some reason Navmii only has maps available for certain countries, mostly in Europe and North America.
    • CoPilot Live Premium: USA, elsewhere
      • CoPilot Live is a very nice, full-featured app, which will let you download maps ahead of time and use GPS offline. I ended up using it because the US version was so cheap compared to the other paid navigation apps, but I've been very pleased with the quality, features, customer support, and free app and map upgrades. It has all the features I could want in a GPS app, the only downsides being you have to have a paid subscription for traffic data (the paid app includes a free one-year subscription), and you will have to buy new maps if you travel outside your purchased area.

      There are detailed reviews of many Android GPS apps here: Android Sat Nav Apps

      I haven't had a chance to try it myself yet, but I've heard good things about Maverick:

      There is both a limited free and pay version.

      It stores OpenStreetMap maps on the phone's storage.

      OsmAnd uses a vectorial format, which means it can store a lot of information without taking too much space, and is visible in all zoom factors.

      You can download the maps you want, for instance Italy, Bolivia, or any other country/region.

      I regularly use Locus. It doesn't have much in the way of navigation support (although I think this is in the works), but for off-road and off-line use it's fantastic.

      It allows downloading of maps for off-line use, supports SQLite and GEMF maps, which allow large map (2GB limit for SQLite, no realistic limit for GEMF) tile sets on your SD card without wasting masses of space. It also supports vector maps as well as bitmap ones (more coverage, less disk space). It has a very good interface and is well supported.

      There's a free version with ads which doesn't support in-app map downloading (I think), although you can use your PC to download the maps. The paid version is not expensive.

      That all sounds excessively glowing, so I should emphasise that I'm not the developer and have no affiliation just a very happy user!


      Building

      "The Blue Book: A Reference Guide for the Nevada Design and Construction Industry" has been updated for 2020. The Nevada Construction Industry Relations Council (NCIRC) completed review and update earlier this year.

      The Blue Book was written to assist building officials, registrants, licensees, and the public in understanding the laws governing building design and construction in Nevada. It is a guideline intended as a source of basic information, referencing the Nevada Revised Statutes (NRS), Nevada Administrative Codes (NAC), building codes, city and county ordinances, board policies, and recommended minimum practices and standards. It also contains a “Frequently Asked Questions” section at the back of the book.

      Members of NCIRC include:
      Nevada State Board of Architecture, Interior Design and Residential Design 
      Nevada State Board of Landscape Architecture 
      Nevada State Contractors Board 
      Nevada State Board of Professional Engineers and Land Surveyors 
      Nevada Organization of Building Officials 
      Nevada State Fire Marshal Division 
      Nevada State Public Works Division

      2018 Northern Nevada Code Amendments by the NNICC

      Basic Wind Speed
      1609.3 Basic wind speed (The ultimate design wind speed, V-ult' in mph)  Amend Section 1609.3 to read as follows:
                           Table Notes:

      Exception: Membrane structures intended to be in place for 30 days or less may be engineered to risk category l loads provided the installation and use are per the manufacturer's recommendations.

      Seismic Design
      I.B.C. Chapter 16, Section 1613 amended:
      The seismic design for structures within Washoe County shall be based on the response parameters and equations of Chapter 16.  See ASCE 7-16 as referenced in the IBC.
      I.R.C. Chapter 3 for single family residential structures: Use Category 'D2'.

      Snow Load Requirements  
      Step 1 - Click on the following link: Geographic Information Systems
      Under Interactive Mapping Application heading, click on: Go To Quick Maps (Please note that Map Warehouse is no longer available).
      If you agree with the disclaimer, click on: "I agree" at the bottom
      You can then enter the property location either by address or assessor parcel number in the upper right had corner.
      When map of the property appears, click on: Show Layers tab to the right, then go to menu on right side and click on theق foot contours.  Zoom in to get elevation number shown on your map/parcel
      If no 2-foot contours show up, Washoe County does not have accurate elevations for your site.  Go back down list and click on 10 Meter USGS Contours.  USGS topo maps may help you to determine your property's elevation.  Please consult your designer.  A Nevada registered surveyor can also determine your property elevation.

      Step 2 - Once you determine the datum elevation of your property, use the following table to determine the design snow load.
      1608.2 Ground Snow Loads Amend Section 1608.2 to read as follows:
      The ground snow load to be used in determining the design snow loads for roofs shall be determined in accordance with Table 1608.2.1:

      Table 1608.2.1

      Note:  This table refers to the old Hwy 395

      1. Drift load design  in the 30 psf zones may utilize ASCE 7-16 table c7-1 ground snow values. 2. The final roof design loads shall not be less than 20 psf after all reductions are factored, except for Lyon & Storey Counties. 3. Intermediate values may be interpolated by proportion.

      Frost Lines, Footings & Foundations
      1809.5  Washoe Counties and the Cities of Reno and Sparks shall be twenty-four inches (24") deep.

       1808.6.1 Foundations.

      Amend Section�.6.1 to read as follows:

      1808.6.1 Foundations. Foundations placed on or within the active zone of expansive soils shall be designed to resist differential volume changes and to prevent structural damage to the supported structure.  Deflection and racking of the supported structure shall be limited to that which will not interfere with the usability and serviceability of the structure.

      Foundations placed below where volume change occur or below expansive soil shall comply with the following provisions:


      Studying the spatial distribution of maximum monthly rainfall in selected regions of Saudi Arabia using geographic information systems

      This paper presents the results of studying the spatial distribution of the maximum monthly rainfall within the Kingdom of Saudi Arabia (KSA) using geographic information systems (GIS). Isohyetal maps were constructed based on long historical rainfall depth data (1963–2013) of 255 rain gauges, after processing the data using different interpolation methods and their conversion to grid raster. Six interpolation methods were used: (a) kriging, (b) spline, (c) natural neighbor, (d) inverse distance weighting (IDW), (e) modified Shepard, and (f) triangulation with linear interpolation (TIN). Estimations of the rainfall at the rain gauges were compared to the observed measurements as controls and the method that resulted in minimum residuals and minimum standard deviation in this case, the IDW was selected for the study. The percentage of residuals within ±2.0 mm were found to be 98 % for IDW, modified Shepard, and TIN, 97 % for natural neighbor, 90 % for spline, and 32 % for kriging. While identifying potential water harvesting sites depends on many factors, such as watershed area, topography, morphology, and rainfall, the results of this study can be used for the primary selection of water harvesting sites based on rainfall being the most important factor.

      This is a preview of subscription content, access via your institution.


      Interactive Map - Communities (Places) and Towns

      To pan: Click left mouse button and hold. Move the mouse to pan across the map.
      To zoom: Use the scroll bar to zoom in and out, or double click to zoom in to a particular location.
      To get information: Click the left mouse button once to select a feature. Additional features can be selected. Click again to unselect feature, or click "Clear Selection" button to clear all feature selections. Data will appear in table below map.
      To download information: After selecting features, click "Save Selection" button to export data for selected features. To export data for all features, click "Save All" button.
      To search: Click next to the magnifying glass in the top right corner of the window. Type in an address, place, or ZIP Code and hit enter.

      Data Source: Fairfax County Department of Management and Budget Economic, Demographic and Statistical Research.
      Note: Fairfax County totals may vary due to rounding.


      Does Gaia GPS work offline?

      Whether your route takes you through busy city streets or to remote mountain peaks, you will always be able to see your current location in the Gaia GPS app.

      1. Connect to the internet to download maps to your device.
      2. Use your device's GPS chip to navigate without an internet connection.

      1. Download Maps

      Gaia GPS lets you download maps directly to your device.

      Downloaded maps save locally to your device for offline access.

      Be sure to download maps before you go on a trip, while you are connected to the internet:

      2. Use GPS

      After downloading maps, you can use your device’s GPS to locate yourself and navigate offline.

      GPS-enabled devices connect to positioning satellites to determine your location.
      Your device does not need an internet connection (cellular or wifi) to provide GPS data to the app.

      These articles will show you how to configure your device's GPS location settings:

      Related articles

      Comments

      This does not appear to be true for the new Apple Watch 3 with GPS+Cellular. Do you know when the GAIA app for Apple Watch 3 will be able to work 100% standalone (e.g. not connected to an iPhone)?

      Gaia GPS currently requires a connection with your main device to display offline maps.

      We don't have any current plans to create a standalone watch app, but please feel free to vote and comment on the feature request for that here: https://help.gaiagps.com/hc/en-us/community/posts/115008813428-Standalone-app-for-Apple-Watch-Series-3-

      Does Gaia GPS able to locate coordinates for any trip?

      @melgararm yes, you can manually import or look up coordinates in the app. You can also save coordinates for anywhere on the map by creating a waypoint.

      It appears with the new "free" level product you are no longer permitted to download maps. is this correct? Based on https://help.gaiagps.com/hc/en-us/articles/115003524547-Free-vs-Membership-vs-Premium-Membership

      Yes, the new version of Gaia GPS that is free to download and a membership is required when downloading an offline map.

      If you purchased the classic version of Gaia GPS, you will receive two free years of Gaia GPS Membership when you log into the new app with your Gaia GPS account.

      Backcountry Navigator allows non paying members to download their basic map for offline use for free. Will Gaia GPS be offering this same feature? I have clients that I would prefer use your app but I do not want them to have to pay for an annual subscription when they may only be using it for a once time trip.

      Thanks for your question, I saw you sent us an email too and Chris has followed up with you there with a few options for your clients.

      To answer your question, though - we don't have any current plans to unlock downloading maps at the free level, but most other features of the app are available for free.

      Having trouble/issues downloading maps for offline use, satellite more specifically.

      1. Some of the time the maps do not actually download 100%, they stop at 90/95% and when I try to resume download - nothing.

      2. At first I was downloading a large area for offline use, when zooming in the imagery was very blurry. I tried to then download zoomed in, much smaller areas to create the wanted large area. still does not help that the images were very pixilated when zoomed in - is there anyway to download offline satellite imagery that is more clear?

      3. Some of the satellite imagery online is not very clear (yes separate section, figured id ask here anyway with my other questions). Is there a reason some locations are more clear than others?

      I'm sorry you are having issues downloading maps. I answered your questions inline below:

      1. Some of the time the maps do not actually download 100%, they stop at 90/95% and when I try to resume download - nothing.

      Can you let me know what map source you are using and the size of the download so I can take a closer look at this issue?

      2. At first I was downloading a large area for offline use, when zooming in the imagery was very blurry. I tried to then download zoomed in, much smaller areas to create the wanted large area. still does not help that the images were very pixilated when zoomed in - is there anyway to download offline satellite imagery that is more clear?

      When downloading maps for offline use, you can use the Max Zoom slide bar to adjust the amount of detail each download will have.

      You can learn more about how to adjust map downloads here for Android or iOS.

      3. Some of the satellite imagery online is not very clear (yes separate section, figured id ask here anyway with my other questions). Is there a reason some locations are more clear than others?

      Unfortunately, due to the process by which satellite maps are created some areas can be clearer than others.

      I recommend checking out different Satellite Imagery maps like Satellite map from MapBox or the World Imagery map if you're a Premium Member


      The limited warranty set forth below is given by Canon U.S.A., Inc. ("Canon") with respect to the Canon imagePROGRAF Large Format Printer packaged with this limited warranty and Canon branded accessories and options designed for use with the imagePROGRAF Large Format Printer (collectively, the "Product"). Canon warrants the Product to be free from defects in workmanship and materials under normal use and service for a period of one (1) year after delivery to the original purchaser (“Purchaser”) by Canon or its authorized dealer. During the relevant warranty period, Canon shall, in its sole discretion and without charge, repair or replace any defective part with a new or comparable rebuilt part or replace the Product with a new or rebuilt Product. Warranty replacement shall not extend the warranty period of the defective Product. This warranty shall not extend to the Canon Printhead for the Product, for which a separate warranty is given. Nor shall this warranty cover other consumable parts or consumables, such as paper and ink cartridges, as to which there shall be no warranty or replacement.
      You must call the number below for remote diagnostic assistance for operation and support of the Product:
       Your local Service Provider or call
       1-800-423-2366, Monday through Friday from 8:00 a.m. to 8:00 p.m. ET
      You must cooperate with Canon in remotely diagnosing the Products malfunction. Canon may attempt to correct the malfunction remotely, with your assistance. If Canon cannot fix your Product’s malfunction through remote diagnostics, Canon shall schedule an on-site service call by an independent authorized Canon Service Provider (the "Service Provider") or Canon will send you a replacement part for any defective user replaceable item. You will be charged at the then-current service call rates of Canon or the Service Provider if the defects in the Product are not covered by this limited warranty, or if the applicable warranty period for the Product has expired or warranty coverage has not been sufficiently established by appropriate documentation.
      This warranty shall only apply if this Product is used in conjunction with compatible computers, peripheral equipment and software, as to which items Canon shall have no responsibility. NON-CANON BRAND COMPUTERS, PERIPHERAL EQUIPMENT AND SOFTWARE WHICH MAY BE DISTRIBUTED WITH THE PRODUCT ARE SOLD AS IS, WITHOUT WARRANTY OF ANY KIND BY CANON, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. The sole warranty, if any, with respect to such non-Canon brand item is given by the manufacturer or producer thereof.
      THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESS OR IMPLIED, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, RELATING TO THE USE OR PERFORMANCE OF THE PRODUCT. NO OTHER EXPRESS WARRANTY OR GUARANTY, EXCEPT AS MENTIONED ABOVE, GIVEN BY ANY PERSON, FIRM OR CORPORATION WITH RESPECT TO THE PRODUCT SHALL BIND CANON OR ANY SERVICE PROVIDER. NO WARRANTY IS GIVEN ON ANY USED PRODUCT.

      THIS WARRANTY SHALL BE VOID AND OF NO FORCE AND EFFECT IF THE PRODUCT IS DAMAGED AS A RESULT OF (A) ABUSE, NEGLECT, MISHANDLING, ALTERATION, ELECTRIC CURRENT FLUCTUATION OR ACCIDENT, (B) IMPROPER USE, INCLUDING FAILURE TO FOLLOW OPERATING OR MAINTENANCE INSTRUCTIONS IN, OR ENVIRONMENTAL CONDITIONS PRESCRIBED IN, CANON’S USER'S GUIDE OR OTHER DOCUMENTATION FOR THE PRODUCT, (C) REPAIR BY OTHER THAN SERVICE REPRESENTATIVES QUALIFIED BY CANON WHO ARE ACTING IN ACCORDANCE WITH CANON’S SERVICE BULLETINS (D) USE OF SUPPLIES OR PARTS (OTHER THAN THOSE DISTRIBUTED BY CANON) WHICH DAMAGE THE PRODUCT OR CAUSE ABNORMALLY FREQUENT SERVICE CALLS OR SERVICE PROBLEMS OR (E) USE OF THE PRODUCT WITH NON-COMPATIBLE COMPUTERS, PERIPHERAL EQUIPMENT OR SOFTWARE, INCLUDING THE USE OF THE PRODUCT IN ANY SYSTEM CONFIGURATION NOT RECOMMENDED IN ANY USER'S GUIDE OR OTHER DOCUMENTATION FOR THE PRODUCT. NOR DOES THIS WARRANTY EXTEND TO ANY PRODUCT ON WHICH THE ORIGINAL IDENTIFICATION MARKS OR SERIAL NUMBERS HAVE BEEN DEFACED, REMOVED, OR ALTERED.

      ANY SYSTEM SOFTWARE (WHETHER FACTORY LOADED ON THE PRODUCT OR CONTAINED ON THE SOFTWARE DISKETTES OR CD-ROM'S ENCLOSED WITH, OR ACCOMPANYING, THE PRODUCT), AND ANY UTILITY SOFTWARE, DISTRIBUTED WITH OR FOR THE PRODUCT, IS SOLD “AS IS” AND WITHOUT WARRANTY BY CANON. THE SOLE WARRANTY WITH RESPECT TO SUCH SOFTWARE IS CONTAINED IN THE SOFTWARE MANUFACTURER'S LICENSE AGREEMENT DISTRIBUTED THEREWITH, INCLUDING ANY LIMITATION AND DISCLAIMERS THEREON. PLEASE CONTACT CANON IMMEDIATELY IF YOU HAVE NOT RECEIVED A COPY OF THE SOFTWARE MANUFACTURER'S LICENSE AGREEMENT.

      NEITHER CANON NOR ANY SERVICE PROVIDER SHALL BE LIABLE FOR PERSONAL INJURY OR PROPERTY DAMAGE (UNLESS CAUSED SOLELY AND DIRECTLY BY THE NEGLIGENCE OF CANON OR ANY SERVICE PROVIDER), LOSS OF REVENUE OR PROFIT, FAILURE T0 REALIZE SAVINGS OR OTHER BENEFITS, LOSS OR CORRUPTION OF DATA INCLUDING, WITHOUT LIMITATION, DATA STORED ON THE PRODUCT'S HARD DISK DRIVE, EXPENDITURES FOR SUBSTITUTE EQUIPMENT OR SERVICES, LOSS OR CORRUPTION OF DATA, STORAGE CHARGES OR OTHER SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES CAUSED BY THE USE, MISUSE OR INABILITY TO USE THE PRODUCT, REGARDLESS OF THE LEGAL THEORY ON WHICH THE CLAIM IS BASED AND EVEN IF CANON OR ANY SERVICE PROVIDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. NOR SHALL RECOVERY OF ANY KIND AGAINST CANON OR ANY SERVICE PROVIDER BE GREATER IN AMOUNT THAN THE PURCHASE PRICE OF THE PRODUCT CAUSING THE ALLEGED DAMAGE. WITHOUT LIMITING THE FOREGOING, THE PURCHASER ASSUMES ALL RISKS AND LIABILITY FOR LOSS, DAMAGE OR INJURY TO PERSONS AND PROPERTY OF THE PURCHASER OR OTHERS, ARISING OUT OF THE POSSESSION, USE, MISUSE OR INABILITY TO USE THE PRODUCT SOLD BY CANON NOT CAUSED SOLELY AND DIRECTLY BY THE NEGLIGENCE OF CANON OR ANY SERVICE PROVIDER. THIS LIMITED WARRANTY SHALL NOT EXTEND TO ANYONE OTHER THAN THE PURCHASER, AND STATES SUCH PURCHASER'S EXCLUSIVE REMEDY.

      Defective parts must be returned to Canon or a Service Provider with all necessary documentation and will become the property of Canon.

      THIS WARRANTY APPLIES TO PRODUCTS SOLD AND USED IN THE U.S.A. ONLY.

      Canon U.S.A., Inc. One Canon Park, Melville, NY 11747 - 3336


      25. The SPC Grid and Map Projections

      Plane coordinate systems pretend the world is flat. Obviously, if you flatten the entire globe to a plane surface, the sizes and shapes of the land masses will be distorted, as will distances and directions between most points. If your area of interest is small enough, however, and if you flatten it cleverly, you can get away with a minimum of distortion. The basic design problem that confronted the geodesists who designed the State Plane Coordinate System, then, was to establish coordinate system zones that were small enough to minimize distortion to an acceptable level, but large enough to be useful.

      The State Plane Coordinate System of 1983 (SPC) is made up of 124 zones that cover the 50 U.S. states. As shown below in Figure 2.26.1, some states are covered with a single zone while others are divided into multiple zones. Each zone is based upon a unique map projection that minimizes distortion in that zone to 1 part in 10,000 or better. In other words, a distance measurement of 10,000 meters will be at worst one meter off (not including instrument error, human error, etc.). The error rate varies across each zone, from zero along the projection's standard lines to the maximum at points farthest from the standard lines. Errors will accrue at a rate much lower than the maximum at most locations within a given SPC zone. SPC zones achieve better accuracy than UTM zones because they cover smaller areas, and so are less susceptible to projection-related distortion.

      Most SPC zones are based on either a Transverse Mercator or Lambert Conic Conformal map projection whose parameters (such as standard line(s) and central meridians) are optimized for each particular zone. "Tall" zones like those in New York state, Illinois, and Idaho are based upon unique Transverse Mercator projections that minimize distortion by running two standard lines north-south on either side of the central meridian of each zone. "Wide" zones like those in Pennsylvania, Kansas, and California are based on unique Lambert Conformal Conic projections that run two standard parallels west-east through each zone. (One of Alaska's zones is based upon an "oblique" variant of the Mercator projection. That means that instead of standard lines parallel to a central meridian, as in the transverse case, the Oblique Mercator runs two standard lines that are tilted so as to minimize distortion along the Alaskan panhandle.)

      The two types of map projections share the property of conformality, which means that angles plotted in the coordinate system are equal to angles measured on the surface of the Earth. As you can imagine, conformality is a useful property for land surveyors, who make their livings measuring angles. (Surveyors measure distances too, but unfortunately there is no map projection that can preserve true distances everywhere within a plane coordinate system.) Let's consider these two types of map projections briefly.

      Like most map projections, the Transverse Mercator projection is actually a mathematical transformation. The illustration below in Figure 2.26.2 may help you understand how the math works. Conceptually, the Transverse Mercator projection transfers positions on the globe to corresponding positions on a cylindrical surface, which is subsequently cut from end to end and flattened. In the illustration, the cylinder is tangent to (touches) the globe along one line, the standard line (specifically, the standard meridian). As shown in the little world map beside the globe and cylinder, scale distortion is minimal along the standard line and increases with distance from it.

      The distortion ellipses plotted in red help us visualize the pattern of scale distortion associated with a generic Transverse Mercator projection. Had no distortion occurred in the process of projecting the map shown below, all of the ellipses would be the same size, and circular in shape. As you can see, the ellipses plotted along the central meridian are all the same size and circular shape. Away from the central meridian, the ellipses steadily increase in size, although their shapes remain uniformly circular. This pattern reflects the fact that scale distortion increases with distance from the standard line. Furthermore, the ellipses reveal that the character of distortion associated with this projection is that shapes of features as they appear on a globe are preserved while their relative sizes are distorted. By preserving true angles, conformal projections like the Mercator (including its transverse and oblique variants) also preserve shapes.

      SPC zones that trend west to east (including Pennsylvania's) are based on unique Lambert Conformal Conic projections. Instead of the cylindrical projection surface used by projections like the Mercator, the Lambert Conformal Conic and map projections like it employ conical projection surfaces like the one shown below in Figure 2.26.3. Notice the two lines at which the globe and the cone intersect. Both of these are standard lines specifically, standard parallels. The latitudes of the standard parallels selected for each SPC zones minimize scale distortion throughout that zone.


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