Have you written a Google Maps mashup using topographic map tiles? Or would you like to? If so, then you will be interested to know that the USGS 7.5ʺ topographic maps, as well as other scales, are available as tiles via free APIs from either Terraserver or the MyTopo company.
Since the MyTopo people have apparently not been doing much to point out their freebie, many developers do not know about this option or how it compares to Terraserver. Below is (1) a method you can use to compare map tile quality and (2) details on using the MyTopo API. I have no connection to either Terraserver or MyTopo. I’m just someone that wants to use the best tool for the job. Tile quality comparison Here are instructions for placing a Terraserver map in one browser tab and a MyTopo map for the exact same area in a second tab. You can then flip back and forth between the tabs and compare the relative quality of the two sets of map tiles. You can use any map center (lat,lon WGS84) for this test. The map center in this example will show a map for the Old Faithful area at Yellowstone National Park. Make your browser full screen 1. Open this site: http://mapper.acme.com/ 2. Enter this coordinate in the search window 44.461721,-110.832396 and click Find 3. Adjust the marker on the zoom control so it is on the 4th cross bar from the top 4. If the topographic maps are not already displayed, then click Topo You are looking at the Terraserver tiles. 5. In a new browser tab, open this: http://www.mappingsupport.com/p/gmap4.php?ll=44.461721,-110.832396&z=14 You are looking at the MyTopo tiles. Since the two maps should now have the same center and same scale you can easily flip back and forth between the two tabs and compare the relative quality of the map tiles. To repeat the test at any other point, just substitute your favorite coordinate. Sidebar: I own the site MappingSupport and the MyTopo tiles are being displayed by a map viewing tool I wrote called Gmap4. Gmap4 is a free, no ads, public service that anyone is welcome to use. This is not a true mashup since it does not display any of my data. Instead, Gmap4 is a general map viewing tool that can display any GPX or KML file that anyone has hosted anywhere. (Support for KMZ files is on the enhancement list.) GPX/txt and KML/txt files can be hosted as Google Documents. If you would like more info, please see the ‘help’ file. In addition to a better quality image on the screen, the MyTopo tiles include the numerous updates the US Forest Service has made to the USGS maps. Here is an example of an updated map for the Government Camp area of Mt. Hood, OR. Note the Forest Service road numbers on the map. http://www.mappingsupport.com/p/gmap4.php?ll=45.295902,-121.730061 It is also easy to find examples of newer roads in national forests that appear on the MyTopo maps but not on the Terraserver maps. Also, if you use the MyTopo API then your mashup can display the 1:50,000 scale topographic maps for Canada. If you already have a mashup using Terraserver tiles and decide to switch to MyTopo, it might be wise to simply comment out your Terraserver code but leave it in place just in case MyTopo stops offering the service sometime in the future. Information on the MyTopo API Here is the MyTopo Terms of Service (TOS): http://www.mytopo.com/google/ Be sure to scroll down so you see all their info. In particular note that (1) you need to tell them if you will be using their API [[email protected]], (2) there is a prohibition on trying to make money from their tiles, and (3) any of your pages that display their tiles must have a link to the main MyTopo page and a link to their TOS. Sidebar: The MyTopo company makes most of their money by selling prints of topo maps that you design. I ordered one just to see what it was like. The quality is every bit as good as an original USGS paper map. In fact, it’s better since it is on waterproof paper and has the current magnetic declination. Since the MyTopo company is generously letting us developers use their API for free, please consider sending some business their way if you and/or your clients need to purchase paper maps. The MyTopo TOS provides this link to their API details: http://www.mytopo.com/google/mytopo.js If your mashup already uses Terraserver tiles then one of the first things you will notice is that MyTopo uses a different tile naming system. For a bit of background on tile naming systems, see: http://www.maptiler.org/google-maps-coordinates-tile-bounds-projection/ The Gmap4 map viewer uses the non-AJAX Google Map API. If you open Gmap4 (see link above) and View==>Source you will find code related to MyTopo in two spots. 1. CustomGetTileUrl2=function(a,b,c) { ..... 2. function initialize_map() { look for a block of code beginning: masu.topo_copy = ...... Note the MyTopo attribution info included in the code. There are plenty of comments in the code to help you find your way around. Time to ’fess up. I previously noted here that I’m aware Pamela has posted coding standards for javascript. Obviously I have not had a chance yet to transmogrify my code into those standards. If you are using the Google AJAX API and wish to use the MyTopo tiles, then please see this post by Chris Schneider and follow his second link. Chris is inviting anyone who needs it to copy some code he wrote for AJAX. http://groups.google.com/group/google-maps-api/browse_thread/thread/5f450e2d8dac3d0e/f35b1afadb4b708c?lnk=gst&q=elfelt#f35b1afadb4b708c Finally, I would simply enjoy knowing if anyone decides to implement the MyTopo tiles. You can email me through my website: http://www.mappingsupport.com/contact.html Thanks for reading. Joseph Elfelt -- You received this message because you are subscribed to the Google Groups "Google Maps API" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-maps-api?hl=en.
