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5

As per whuber's comment: differentiating with respect to the angular coordinates is incorrect, i.e. it is not a conformal map between (lat,lon) and (x,y) map coordinates; instead it is a local mapping from (local) easterly, northerly displacement onto map displacements. Thus, you need to differentiate w.r.t. easterly and northerly displacements in meters ...


4

When geographic coordinates are plotted "without projection", they are really being projected via the Simple Cylindrical (aka, Equirectangular, or Plate CarrĂ©e) projection. (It goes by many different names.) Geographic coordinates, as latitudes and longitudes, are said to be unprojected because they define positions on a (curved) sphere or ellipsoid – ...


3

Proposal: Conic Equidistant Projection This preserves distance over all meridians and two parallels of choice (could be optimized for major areas of interest). Notice, most distance distortion is in the southern oceans out of the area of interest. As an alternative, you could divide the world into 5 identical projections centered on each continent. This ...


2

If you compare your input and what the service sends back for EPSG:3857 you can indeed see many differences, for example: DATUM["World Geodetic System 1984", DATUM["WGS_1984" PROJECTION["Popular Visualisation Pseudo Mercator", AUTHORITY["EPSG","1024"]] PROJECTION["Mercator_1SP"] So you were right with your guess "Or PostGIS stores SRText differently ...


2

Either the WGS 1984 in the original raster, or in the target UTM doesn't match Esri's definition of WGS 1984. It's probably one of the names. If it's the original raster, try using the Define Projection tool to reset it to Esri's WGS 1984 definition. If it's the output coordinate system, try using Esri's version instead.


2

The shapefile distributed by GeoDa Center does not have a PRJ file, so normally you would have to define the projection in order to line it up with other spatial data. But it appears that while the shapefile distributed by GeoDa Center does in fact use the UTM 19N zone, for some reason the units are in kilometers, where UTM coordinates are usually expressed ...


2

See my solution for QGIS: Export your projects to shape, and load them to qgis. If you want to use meter for your buffer distances, you have to transform your layer to meter coordinate system. The Best would be the local (country-national) coordinate systems. So save as your layers again to shape but in the CRS section choose selected CRS and load your new ...


2

Unless you really need ~millimeter accuracy you do not need a custom local system. Just use the appropriate UTM zone. UTM is metric and projected, so you will get proper distances. You can find some examples for calculating the distortion from going away from the central meridian of an UTM zone. You can keep your source data as WGS84 but be aware that at ...


1

You're thinking in cartesian and operating in geodetics. If you really want to do delta_x/delta_y, do the work in in geometry in some projected space, not geography. If you want to use geography, don't use delta_x/delta_y, use distance/direction, generated using ST_Distance(geog,geog) and ST_Azimuth(geog,geog). (It's sometimes hard to visualize, but if you ...


1

From the top screenshot, it would appear that the projection/coordinate system for your original file is incorrect (or has been incorrectly defined). The display units in the bottom right of the screen indicate decimal degrees, but the XY values are not a possible combination for GCS 1983. This combination of XY values and decimal degree units can only ...


1

I guess your data have lat/long coordinates ("Geographic coordinate systems" in ArcGis), so that coordinates are stored in degrees (e.g. decimal degrees). For this kind of analysis I think the use of a "Projected coordinate systems" is recommended. You can refer to the following image (Wikipedia) to find the UTM zone where your project data belongs: ...


1

You simply can't because it's not possible for the browser to reproject images from Spherical Mercator (MapQuest) to UTM at the moment. You will need an intermediate server to reproject MapQuest tiles like Mapproxy. Be aware that tiles with labels, with reprojection deformation, will be less readable. FYI, Proj4.js is useful only to reproject vector layers. ...


1

To use any formula, you need the parameters of the Albers Equal Area projection: latitude and longitude of origin first and second parallel You can guess the longitude from the only meridian that is straightly vertical, but the others are more difficult to get. You might be better off by using a georeferencing tool. The georeferencer inside QGIS does a ...


1

if you want to set the projection of a file with gdal tools, you should use gdal_edit.py -a_srs Both gdalwarp and gdal_translate will create a new file.


1

Normally, no, you cannot just change the SRID value. SRID stands for Spatial Reference System Identifier and is a coded value describing what coordinate system the data's geometry is in. Let's take the example of the two CRS (coordinate reference systems) you have. 4326 is WGS84, which is a geographic CRS with degrees for units and the WGS84 datum. 27700 is ...


1

There are many possible solutions, but a convenient and accessible way will be to use an appropriate projection. What properties must it have? It should be conformal (or very nearly so throughout the region of interest). This means there is no relative scale distortion as the bearing is varied around any fixed point but--necessarily--there will be ...



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