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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1answer
5k views

How to define new custom projections in QGIS?

I'm trying to define a projection in QGIS. I want to add North America Albers Equal Area Conic. From the spatialreference site I copied the proj4 line: +proj=aea +lat_1=20 +lat_2=60 +lat_0=40 ...
2
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4answers
3k views

OpenLayers transform EPSG 27700 coordinate to Google 900913

Community, I'm currelty capturing my mouse click event and trying to transform the coordinates into Long Lat. I need to get at the Long Lat as strings so I can build a url and throw it at Google ...
2
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1answer
1k views

How can I transform GCS_WGS_1984 to GCS_North_American_1983?

I need to convert a GCS_WGS_1984 data set to NAD_1983_UTM_Zone_14N. What transformation should I use?
1
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1answer
544 views

Converting distance between nautical miles and degrees

This is such a basic question that I'm kinda of embarassed. Here is the situation: We have a certain funcionality developed that: Will check for a tolerance value (this input is given by the user ...
1
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1answer
475 views

Defining multiple projections inside a file gdb [error 000289 failed to alter spatial reference]

I am importing multiple shapefiles into a filegdb in ArcGIS 10, and using the following code to define the projection of the feature once imported, to the .prj of the original .shp file. Here is my ...
2
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1answer
378 views

Possible to use Google Earth to generate “skyline” planes?

I was really interested to notice that my city appears to have gotten the 3D Buildings treatment on Google Earth. I am trying to figure out how I might these 3D buildings to generate 'skylines' for a ...
4
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5answers
3k views

How to add a projection to a Shapefile using open-source tools?

I have been given some shapefiles WITHOUT a projection. So I need to add the projection in order to display it on google map. I found the projection information I need at ...
11
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7answers
385 views

Public reprojection services

Are there any free public services where I can send one point in a coordsystem and it returns the point reprojected in a specified coordinate system? I will not be doing many requests, for now it is ...
1
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1answer
326 views

Best practices to minimize error when buffering unprojected data

If I buffer hundreds of unprojected WGS84 points across the US by say, 3 miles, will I get accurate areas returned (3 x pi x r) for each of the circles created? I suspect not. If not, what would be ...
1
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1answer
574 views

Choosing best projection/SRID

I created a shape in OpenJump and exported it to shape(ESRI) file and then imported it to SQL2008 via shape2sql , the problem is that it shows bigger than what I want, In OpenJump it shows 1meter ...
9
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2answers
3k views

Measuring distance in spherical Mercator vs zoned UTM

I've got points in WGS84 lat/long and I'd like to measure "small" (less than say 5km) distances between them. I can use the haversine formula from http://www.movable-type.co.uk/scripts/latlong.html ...
2
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1answer
1k views

Quantum GIS Reproject a projected coordinate system with rotation

I have two shapefiles:- one in WGS84 Z30S and one in a custom, system based, projection. I need to convert the custom projection into WGS84 Z30S. I have a set of parameters including a shift in X and ...
2
votes
1answer
785 views

Overlapping map tiles with mapnik's generate_tiles.py script

I'm trying to generate map tiles using the mapnik's generate_tiles.py script, but the resulting tiles are overlapped. Example The tiles have the following directory structure: ...
1
vote
0answers
643 views

mixing lon/lat and mercator layers in a MapServer .map file

I have a basic question about my MapServer .map file, which has two layers, each with a different coordinate system, longlat vs. mercator. See my .map file below. If I leave it as shown below, with ...
28
votes
2answers
954 views

What projection appeared in the NYTimes this morning?

Perhaps not as GIS related as some, but definitely about maps. Can anyone identify the map projection that appeared in the New York Times this morning? It's not one I've seen before, and a quick ...
9
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2answers
520 views

Is there a way to draw a straight line on a map which also represents a straight line on the earth surface?

I'm trying to understand more on projections. In this example, why must one calculate the curvature of the earth (great circle) if the map is already projected? Is there a way to draw a visibly ...
1
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0answers
86 views

List of methods of determining the projection of a shapefile when .prj is missing [duplicate]

Possible Duplicate: Best practices for identifying the unknown coordinate system of a Shapefile It would be helpful to mention what information is needed to perform each technique. What are ...
2
votes
1answer
182 views

OpenLayers.Control.DrawFeature Accuracy problem

When i draw a polygon using the OpenLayers.Control.DrawFeature then i export that polygon to KML using OpenLayers.Format.KML. Though, when I open it in google earth there is a big difference between ...
6
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1answer
814 views

projection/pyproj puzzle, and understanding SRS format

I have a shapefile that has a .prj file, with the following wkt contents: ...
2
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0answers
482 views

Arc by center point in PostGIS does not fit the circle

I'd like to store a GML ArcByCenterPoint in PostGIS. I can work out the start, middle and end points required by the CIRCULARSTRING type and all seems to be OK, except that when I visualise the arc it ...
46
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8answers
2k views

One dimensional map of the world?

Bit of a strange question but hope this is OK to ask here. Has anyone heard of a '1-dimensional' projection of the world map - that is mapping all the points on the globe to a single line? I was ...
3
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2answers
169 views

Can you search WMS services for a particular projection?

Is there an interface or website to search public WMS services for location/projection?
4
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2answers
7k views

Using ArcMap, how may I convert a shapefile to use decimal degrees?

I have a shapefile that currently uses meters as the measure for its coordinate system, but the map framework I wish to use expects decimal degrees. I'd like to reproject my shapefile to use decimal ...
3
votes
2answers
2k views

How to set spatial reference to OSGB_1936_British_National_Grid in ArcGIS

I have two datasets in ArcGIS. One is from the Ordnance Survey (UK National Mapping Agency) and, when I view the properties of the dataset it says that the Spatial Reference is ...
2
votes
1answer
317 views

Reproject TM65 to OSGB in ArcGIS

I have a TIFF file in the TM65 (Transverse Mercator) projection, and want to convert it to the OSGB (British National Grid) projection. I'm trying to do this in ArcGIS using the Project Raster tool. ...
25
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3answers
546 views

Why are Data Projections relevant?

Sorry for my ignorance - especially after being in this area for a long time. Why is it useful to store data in unusual projections and datums? I understand the value of projections as output ...
3
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2answers
447 views

Project twitter geo data into wgs 84 map

I'm currently working on displaying twitter geo data (currently just long/lat -> cartesian without any analysis). This is the world map (source: naturalearthdata): ...
4
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1answer
2k views

What's up with the GeoJSON spec and CRS as a IRM?

I'm writing a web API to our GIS data, currently revamping our geocoding service. I'm creating the option for folks to specify the output type as GeoJSON so I'm trying to follow the spec. Our data is ...
2
votes
1answer
132 views

Projection Decision

I'm deciding on whether to use a geographic projection (lat/long) or a lambert conformal conic projection for a web servicing project that will use raster, vector, and point data, for queries, ...
6
votes
1answer
472 views

How does OpenLayers determine a layer's projection?

Could anyone explain the strategy OpenLayers take to determine the layer's projection? For example, if I didn't explicitly specify any projection for a marker layer, what projection would the layer ...
6
votes
1answer
198 views

What is the definition for a geographic coordinate system with east/west bounds of 0 to 360

I need the coordinate system reference or a projection definition that uses geographic (i.e. lat/lon) coordinates but instead of east/west bounds being defined as 180 to -180, I need them to be ...
20
votes
2answers
1k views

What projections should I use to make my own Globe?

Searching for an answer to this question, I found instructions posted by Gulf of Maine Research Institute showing how to create a globe. Using manual methods ... What approach would I take to ...
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1answer
497 views

How to calculate oblique photo scale?

Is it possible to calculate oblique photo scale by given vertical photo scale ? I mean is there any kind formula relation between them or maybe is it possible to calculate rough approximation of ...
5
votes
4answers
2k views

Automate Projection of multiple shp files using ArcPy

I have been trying to create a Python script that will convert all shape files within a folder from GCS WGS 84 to Web Mercator. Below is the code I have so far but what I'm struggling with is how to ...
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 ...
3
votes
1answer
327 views

Ogr2ogr projection problem- features are shifted 12 miles to the north?

I have discovered a problem related to the output of an ogr2ogr command line call. My resulting polygon features are 12 miles (.18 degrees) due north of where they should be, but the longitude is ...
36
votes
3answers
12k 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 ...
0
votes
1answer
1k views

QGIS and MapInfo Projections - EPSG 27700 (British National Grid)

I have some data in a PostGIS table with the projection EPSG 27700. If I export this data from QGIS (v1.8) to MapInfo TAB / MIF when I open the data in MapInfo it has a shift on it. Does anyone know ...
1
vote
1answer
410 views

Issues with defining projection to that of the current root file

I am creating a shp file with the extent of all the raster file in a set of directories and it works fine when all the rasters are in the same projection but not when they switch around. So I want to ...
10
votes
4answers
2k views

How to reproject spatial data using free libraries?

How can I use free libraries to transform spatial data? For example, I want to change the projection of a Shapefile within the code of my C# web application. How do I do that?
5
votes
0answers
100 views

Is there a tool to retrieve the projection system used to create a shapefile when the prj file is missing? [duplicate]

Possible Duplicate: .shp with unknown coordinate system Are there any tools to help retrieving the projection system used to create a shapefile when there is no .prj file? Given that ...
2
votes
1answer
473 views

How to determine area of pixel in meters with GDAL and Python?

I have a raster loaded in Python using GDAL bindings. I'd like to be able to determine the area of a pixel in meters although I'm not confident that the projection is in meters. On this page I see a ...
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 ...
20
votes
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 ...
1
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1answer
235 views

Lambert cylindrical projection support in PostGis

Does PostGis support Lambert cylindrical projection or is there a way to add support for it? I'm probably searching the wrong terms, but google isn't bringing up anything useful. Any help is ...
5
votes
2answers
306 views

Does the Chamberlin trimetric projection map (some) great circles to straight lines?

I know that, in general, the Chamberlin trimetric projection maps most great circles on the sphere to some sort of non-straight curve on the flat map. But what about the 3 special great circles ...
3
votes
1answer
485 views

How to generate a grid of horizontal equal-area rectangles in a Mercator projection?

I'm new to GIS so pardon my ignorance and bear with me. I'm generating a grid relative to a LonLat point. To make the cells all equal area, I'm creating it in 2163 projection. The problem is that when ...
1
vote
1answer
146 views

Get relative north aligned point 2163 (US Equal Area)

What I'm trying to do is create a grid where the y axis is north aligned. I have a origin Lat/Lon point which is the bottom left corner of the grid and each cell should be 100 by 100 meters. So I ...
1
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2answers
655 views

Can I project 3D DXF vertical cross section into a “plan view projection plane” for display in ArcMap?

Below is the lenghty explanation but simply put my question is: How can I project a 3D DXF file (vertical cross section) into a "plan view projection" for use in ArcMap? I am using Target (by ...
4
votes
1answer
2k views

Is there a simple way to compute the UTM Zone from a lat/long point?

I am trying to convert a latlong point to UTM. To define UTM projection, I need to calculate zone for the point. I am trying to figure out the best way to do this. One way to do this would be use ...