Gmap4 has been updated to version 1.9.1 dated January 17, 2011. This version adds support for UTM coordinate grids
. All UTM support in Gmap4 uses the WGS84 datum. This UTM support works worldwide
. For more info on UTM coordinates see: http://en.wikipedia.org/wiki/Universal_Transverse_Mercator_coordinate_system(Pay back time: When you visit other outdoor-related forums, please do a search and see if Gmap4 has been mentioned. If not, it would just take a moment for you to pass the word along. Also, are you doing the social network thing? Consider saying something nice about Gmap4.)
Here’s a map of Grand Canyon Village with a UTM grid. http://www.mappingsupport.com/p/gmap4.php?ll=36.059592,-112.139836&t=t2&z=14&coord=utm
To toggle UTM support on and off, click Menu ==> UTM On/Off. If UTM is ‘on’ then Gmap4 gives you UTM information in three ways:
1. A UTM grid is displayed. This UTM grid is displayed on both the MyTopo topographic maps (USA and Canada) and the standard views (aerial, etc) provided by Google Maps.
2. The lower right corner of the screen will always show the UTM zone and UTM coordinates for both the cursor and map center.
3. You can get the UTM zone and coordinates for any point on the map by right-clicking that point.Things to keep in mind
You can build you own map links by using URL parameters. If you want your map to appear on the user’s screen and already have UTM turned on, then add this URL parameter: &coord=utm
Here is a comparison:
With UTM on http://www.mappingsupport.com/p/gmap4.ph...2&coord=utm
With UTM off (default) http://www.mappingsupport.com/p/gmap4.ph...ek.kml&t=t2
If you zoom out far enough then you will not see a UTM grid. Instead you will only see vertical red lines
which mark the edges of the UTM zones.
UTM grid lines that are near the edge of their zone often appear curved when displayed using the map projection used by Google Maps. The grid lines in the adjoining zone will curve in the opposite direction. For example, the next map is centered near Lake Tahoe. The red line marks the edge of adjoining UTM zones. Double click each side of the red line (this changes the map center) and watch the UTM grid lines change. The grid lines are calculated based on the UTM zone that contains the center of the map. http://www.mappingsupport.com/p/gmap4.php?ll=39.115536,-120.208437&t=m&z=8&coord=utm
Some MyTopo topographic maps already have a UTM grid printed on them. Caution! Some of those printed grids are based on the older datum NAD27. Those older grids will have a uniform offset from the grid displayed by Gmap4 which is based on datum WGS84 . For example: Here is a map showing part of the Alpine Lakes Wilderness area in Washington State where the MyTopo maps have a UTM grid based on the WGS84 datum. Click Menu ==> UTM On/Off and you will see the faint UTM grid printed on the map: http://www.mappingsupport.com/p/gmap4.php?ll=47.47229,-120.80588&t=t2&z=14&coord=utm
By contrast, here is a map showing part of the Yosemite Valley area in California, where the MyTopo maps have a UTM grid based on NAD27. Note the uniform offset between the two sets of grid lines. http://www.mappingsupport.com/p/gmap4.php?ll=37.736733,-119.568449&t=t2&z=14&coord=utm
Usually (but not always) the different zoom levels use a different scale for the UTM grid. To learn the grid scale, compare the cursor coordinates (lower right corner) as you point to adjacent grid lines. If you want to know the zoom level, right click the map.Maps with UTM grid lines can be printed.
File ==> Print Preview
If you know of any other map viewing software that can display the MyTopo topographic maps along with a UTM grid, I would enjoy knowing about it.Future UTM improvements
There are different methods for putting labels on the grid lines. I am pondering what will work best.
Another possible improvement is to let the user change the line width, color and/or spacing.
Other ideas?Next Gmap4 update
Bad news: The ‘Search’ feature of Gmap4 no longer works very well for placenames. This feature uses Google’s ‘geocoding’ service on the backend. OK, I admit it. Gmap4 was pushing the envelope in its use of that service. Whoops - Google pushed back. Guess who won? I will add a second search tool that is designed to work well with placenames.
Good news: The existing ‘Search’ feature of Gmap4 still works fine for searching on (1) anything related to addresses including names of many settlements that no longer exist and (2) any reasonable way to write a latitude/longitude pair.
Finally, if you find Gmap4 to be useful I hope you can take a moment and do some ‘pay-back
’ by letting other people know about it.
Joseph - Gmap4 author