The process of converting the coordinates of a map or an image from one system to another, typically by shifting, rotating, scaling, skewing, or projecting them.

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14
votes
3answers
2k views

Rubber sheeting in GRASS or QGIS

We are in the process of getting our property boundaries corrected and a side effect of this is that we need to move any assets that have been drawn relative to the property boundaries, so they are ...
6
votes
3answers
789 views

Retrieve polygon smallest MBR

I have a postgis table containing polygons. I want to transform my polygons to 4 points polygons : retrieve the smallest MBR. Here comes an illustration of what I want : My original polygon is ...
7
votes
1answer
2k views

How do I get a country border data set into my geography column?

I have a PostGis database with a multipolygon geography (as opposed to geometry) column. I'd like to fill it with the country border data available from ...
3
votes
1answer
673 views

Ordnance Survey data to WGS-84

Recently I have reprojected Ordnance Survey data from British National Grid (ORD SURV GB) to WGS-84 using ArcGIS 9.2. After re-projecting I have found some shift in the data. Can any body guide me ...
5
votes
2answers
591 views

Why are the coordinates transformed with proj.4 off compared to http://valdemar.kms.dk/trf/?

I am trying to transform from epsg:4326 (wgs84) to epsg:25832 (utm ETRS89) using Proj.4. I am comparing the results with results from http://valdemar.kms.dk/trf/ . it seems like the results ...
3
votes
1answer
299 views

Is a WMS map always a constant scale?

If I get a map back from a WMS server is the scale always constant over them map regardless of the reference system? So if I have a map which is 100 pixels wide, will the point at 50 pixels always ...
3
votes
2answers
875 views

Which ESRI defined geographic transformation do I need to use to convert my “ NAD83 Northern Virginia” data into WGS 1984 Web Mercator?

My title pretty much tells it all.. I have a number of datasets in which I want to batch project from NAD83 Northern Virginia Datum into the correct Web Mercator projection.. When I do a straight ...
11
votes
6answers
584 views

Where can I find GIS data to test GIS coordinate operations?

I am trying to find some data that can be used to test GIS coordinate operations from one CRS to another CRS. So far all I have found is the Gold Data set and also various example points in the EPSG ...
5
votes
5answers
6k views

How to convert coordinates from Gauss-Krueger to Longitude/Latitude?

I'm a newbie in the GIS world so please advise me :) In my .NET/C# project I need to show some shapes/points on the Bing Map. The problem is I have the Gauss-Krueger coordinates and need to convert ...
1
vote
2answers
426 views

CORS - HARN transformations - what is the most accurate method

This may not be an issue for many GIS-ers but has anyone else had experiences transforming from modern NAD83 (CORS) to HARN coordinates and vice versa? I realize the discrepancy might be something ...
2
votes
1answer
444 views

How to convert SHP/POSTGIS data into x, y, z, “cost” data?

Is there a way to convert a line layer (shp or PostGIS) data into (x, y , z, cost) i.e. (From_node, To_node, optional_Elevation, Cost/Weight) ?