Recently I added a UTM grid to my v3 app “Gmap4”. Below is a demo and a brief description of the approach I used.
Here is a Google Terrain map of the world showing the edges of the UTM zones (WGS84 datum). After you zoom in enough, then a UTM grid will appear. To search, click Menu ==> Search http://www.mappingsupport.com/p/gmap4.php?ll=27.717297,7.832677&t=t1&z=2&coord=utm The lower right corner of the screen displays the UTM coordinates for the cursor and map center. To toggle the UTM grid, click Menu ==> UTM On/Off. I am not using a custom map projection. Instead, the UTM grid is simply comprised of a number of polylines. Each grid covers an area roughly 20-30% larger than the image on the screen. Each time the map is panned/zoomed the polylines are cleared and then recalculated. I am not using any of the Proj.4 libraries. Instead, my code simply includes the essential formulas to convert back and forth between lat/ lng and UTM. Performance, at least on my ~3 year old PC, is certainly acceptable. One of the challenges was managing the listeners that Gmap4 uses so that when the map was panned/zoomed for any reason (1) the old grid was erased and (2) a new grid was drawn only once. If you are curious about Gmap4, the homepage has examples, links to sites using Gmap4, a detailed Help file and a bit about me. http://www.mappingsupport.com/p/gmap4.html Joseph - Gmap4 author Redmond, WA -- You received this message because you are subscribed to the Google Groups "Google Maps JavaScript API v3" 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-js-api-v3?hl=en.
