A map projection is any method of representing the surface of a sphere or other three-dimensional body on a plane

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4
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1answer
406 views

what are the main advantages of using a Double Stereo projection?

I'm not per say a GIS guru, I'm more of a user of the technology. On a recent project we were asked to analyze, provide, and submit all our analysis using a Double Stereo projection. What are the main ...
21
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3answers
2k views

What was the rationale for the non-standard UTM zones near Norway?

UTM zones 30V, 31V, 32V, 31X, 33X, 35X, and 37X do not line up with the rest of the UTM zone grid. Why was this allowed? According to Wikipedia, UTM was developed by the U.S. Army Corps of ...
5
votes
2answers
662 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 ...
30
votes
2answers
1k views

What coordinate system should be used to store geography data for celestial coordinates?

I am doing an astronomy project. I want to have the information about our images stored in a spatially enabled database. This, I would think, should be a very easy special case for GIS functions ...
14
votes
5answers
2k views

Does Re-Projecting ShapeFile only update content of *.prj file?

if i wish to change the projection of some shapefiles from .. lets say NAD83 (4269) to WGS84 (4326) ... and by using some 3rd party app .... does this mean the .prj file is only updated .. and not the ...
4
votes
1answer
302 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
949 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
644 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
1answer
674 views

What is north-up projection?

How do I know what projection to use for north-up or 0 rotation? I have a gtiff (ND83-nf) that gives me the error when importing to Grass. Should I re-project or recreate the image with the rotation ...
2
votes
1answer
2k views

How can I convert from EUREF-FIN coords to Lat/Long?

See question title, how can I Translate EUREF-FIN coords to Lat Long?
2
votes
3answers
3k views

How to change default projection in ArcPad 10?

Is there a way to set a default projection in ArcPad 10? The only way I can tell is by creating a quickProject based on a project that contains a shapefile with the same projection, but that's just ...
19
votes
10answers
3k views

Discontinuous or Interrupted map projections?

Do any of the current open source GIS softwares support discontinous projection systems? E.g. sinusoidal, dymaxion, butterfly, etc? If not, are there any affordable commercial ones that do (affordable ...
4
votes
3answers
3k views

Parameters for ED50 -> ETRS89/WGS84 seven-parameter transformation which are good for Denmark?

I am looking for parameters for a seven-parameter transformation (Rx, Ry, Rz, Tx, Ty, Tz, s) from ED50 UTM (zone 32U) to ETRS89 and/or WGS84. The best match I could find is here: ...
3
votes
2answers
339 views

How does ESRI, and how should anyone, transform a coordinate that lies outside a grid transform (e.g. NADCON)?

As I understand it, a datum transform (e.g. urn:ogc:def:coordinateOperation:EPSG::1241) based on a grid interpolation method, e.g. NADCON, is undefined outside of the grid of points. Therefore the ...
9
votes
3answers
6k views

How does ArcGIS compute the distance between two points with a non-equidistant projection?

This is a follow-up question to my previous one, Can you suggest some well-written introductory texts about coordinate system projections? Let's assume I'm working with the CH1903 map projection, ...
16
votes
8answers
461 views

Can you suggest some well-written introductory texts about coordinate system projections?

Even after some time working in this GIS field, I still don't have a solid understanding of spatial references, how they are projected, and most importantly, if you still need to worry about the fact ...
1
vote
2answers
372 views

Positional changes bewteen MapInfo 7 and 10

I have just come across something bizarre and I can't explain it. I have programs for creating grid squares and for converting points to polygons based on an OS grid reference [GB BNG]. Recently we ...
5
votes
5answers
7k 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
1answer
1k views

How to convert from ITM ref to GPS ref ?

How can I convert from ITM ref (Israel new map) to GPS ref and from GPS ref to ITM ref? I need any C# sample code or formula for this. For example: 32.086156,34.769239 = 178364,665948 Or : ...
0
votes
3answers
444 views

Need help understanding why gdal projections aren't giving me what I expect?

When using gdaltranslate and gdalwarp I specify the following transfomation (in for GCP's and translate, out for warp) +proj=lcc +lat_1=40.03333333333333 +lat_2=38.73333333333333 +lat_0=38 ...
4
votes
5answers
2k views

How to re-project coordinates in a gml on-the-fly in Geoserver?

I am using Geoserver to get featureinfo, but sometimes I want to re-project the native SRS in the output gml. The request is a (WMS) "GetFeatureInfo" with INFO_FORMAT: application/vnd.ogc.gml. I am ...
5
votes
3answers
292 views

How to manually change from GPS (WGS84) to web based maps projection systems?

I have collected location point data and wish to display this on a web based map. It was collected using a Garmin Etrex GPS using the WGS84 datum. I wish to display the points using Ushahidi and have ...
11
votes
5answers
6k views

How can I measure area from geographic coordinates?

If I have polygons in geographic coordinates (WGS84), how do I measure the total area each takes on the surface of the earth, taking into account the curvature of the earth?
137
votes
11answers
38k views
5
votes
2answers
257 views

Arcmap: Create a projection to emphasize a given direction?

Suppose one had a dataset (centered on a given coordinate) of lines that were very close together in terms of longitude but also had important turns/bends far separated by latitude. In order to map ...
36
votes
3answers
13k views

What is the current Web Mercator projection code?

The web mercator projection, popularised by Google Maps, seems to be given a new EPSG code every couple of years. EPSG:900913 (Google in calculator text) was an unofficial code EPSG:3785 - is the ...
20
votes
5answers
2k views

Simplifying geometries (generalization)

What are the recommended ways of simplifying geometries? Keeping in mind projections, and simplifying state geometries for example. I've heard about converting to an 'equi-distant' projection that ...
20
votes
8answers
19k views

How do I convert State Plane coordinates to latitude-longitude?

Given a specific state plane coordinate system (whether NAD27 or NAD83), are there any resources to convert to latitude-longitude?
5
votes
4answers
13k views

Convert latitude and longitude into northings and eastings

Hi I have the following UK postcode dy8 3xt and know that the latitude and longitude is:- 54.452772 -2.156082 I also know that the Eastings, Northings for the postcode is:- 389490 283880 ...