Is it possible to create a scalebar in ArcMap that shows distances in custom units? I understand how to do this manually, but it would be great if I could define a custom unit of measurement (let's say "1 swimming pool") and use that to dynamically generate a scalebar.
[GIS] Custom scalebar units in ArcMap
arcgis-desktoparcmapscaleunits
Related Solutions
ArcGIS using COGO you can apply 'ground to grid correction'
*ArcEditor or ArcGIS only
Click Ground To Grid Correction on the COGO toolbar.
When you read the COGO descriptions for boundaries on a survey plan or other legal document, the directions and distances are measured on the surface of the earth. These are referred to as ground measurements. However, the directions and distances in your GIS data are based on the spatial data's coordinate system, or the grid measurements. Ground and grid measurements are often different. You may set constants (the ground to grid correction) for directions and distances so that the software can correctly convert between the ground and grid measurements.
Spent quite some time testing, and as usual, the solution is fairly simple once you know how Leaflet wants to work.
The solution is to specify a custom CRS with a custom transform function. This s where you can specify what each map unit/pixel represents, and this is what is used by Leaflet internally for all distance calculations and - well - transforms :) .
Leaflet does neither support changing CRS (Coordinate Reference System) of a map after its been initialized, nor does it support different CRS per layer. This means you have to specify this custom CRS before you initialize the map. Or you have to reinitialize the map when you want to load a different layer: If you need to do that, know that you can use "map.remove()" to properly remove an already initialized map (this function is not documented, so I had to search a bit).
Look at this fiddle for how I fixed the problem fiddle posted in the question:
https://jsfiddle.net/pdqavdup/2/
var factorx = 0.125
var factory = 0.125
L.CRS.pr = L.extend({}, L.CRS.Simple, {
projection: L.Projection.LonLat,
transformation: new L.Transformation(factorx, 0, -factory, 0),
// Changing the transformation is the key part, everything else is the same.
// By specifying a factor, you specify what distance in meters one pixel occupies (as it still is CRS.Simple in all other regards).
// In this case, I have a tile layer with 256px pieces, so Leaflet thinks it's only 256 meters wide.
// I know the map is supposed to be 2048x2048 meters, so I specify a factor of 0.125 to multiply in both directions.
// In the actual project, I compute all that from the gdal2tiles tilemapresources.xml,
// which gives the necessary information about tilesizes, total bounds and units-per-pixel at different levels.
// Scale, zoom and distance are entirely unchanged from CRS.Simple
scale: function(zoom) {
return Math.pow(2, zoom);
},
zoom: function(scale) {
return Math.log(scale) / Math.LN2;
},
distance: function(latlng1, latlng2) {
var dx = latlng2.lng - latlng1.lng,
dy = latlng2.lat - latlng1.lat;
return Math.sqrt(dx * dx + dy * dy);
},
infinite: true
});
var MAP = L.map('map', {
crs: L.CRS.pr
}).setView([0, 0], 2);
var mapheight = 2048;
var mapwidth = 2048;
var sw = MAP.unproject([0, mapheight], 4); // Level 4, because this is the level where meters-per-pixel is exactly 1
var ne = MAP.unproject([mapwidth, 0], 4);
var layerbounds = new L.LatLngBounds(sw, ne);
var mapname = "beirut"
var mapimage = L.tileLayer('http://tournament.realitymod.com/mapviewer/tiles/' + mapname + '/{z}/{x}/{y}.jpg', {
minZoom: 0,
maxZoom: 5,
bounds: layerbounds,
noWrap: true,
attribution: '<a href="http://tournament.realitymod.com/showthread.php?t=34254">Project Reality Tournament</a>'
})
mapimage.addTo(MAP);
L.control.scale({
imperial: false
}).addTo(MAP);
Best Answer
You could do it by defining your own projection;