I am confused about projection and getting my scale/measurements to match our
existing map. I am a complete noob when it comes to projection and
coordinate systems and really have no idea what I'm doing. All I know is our
existing map application is using 3TM-114. When I open this file it says -
Projection, Transverse Mercator, North American 1983, GRS80. When I use the
WMS service provided by our applications it is being output into EPSG:4326.
When using openlayers I am trying to get the measurements/scale the same as
our existing maps but it is way off. I am declaring my map as the following
-
// begin map defintion
map = new OpenLayers.Map('map',{controls: [],
maxExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34,
20037508.34, 20037508.34),
maxResolution: 156543.0399,
numZoomLevels: 20,
units: 'km',
projection: new OpenLayers.Projection("EPSG:900913"),
displayProjection: new OpenLayers.Projection("EPSG:4326")
}); //end of map definition
I realize this is using display projection of EPSG:4326 except when I use a
scale control or mouse position control and move to the same locations as
our existing map it is no where near the same. I have been exploring using
Proj4JS on the client side but I am not sure if this is what I should do. Is
there another transformation option I should be using on my WMS layers
directly or will proj4 do this and allow me to measure distance, area and
show scale properly after I do some transformations? I greatly appreciate
any suggestions.
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