Questions tagged [coordinate-system]

A reference framework consisting of a set of points, lines, and/or surfaces, and a set of rules, used to define the positions of points in space in either two or three dimensions. This tag also refers to cartographic projections and coordinate system transformations.

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12
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2answers
5k views

What is the standard Mercator projection?

I'm using QGIS in order to re-project a shapefile I have into "Mercator" so that something like protoviz understands my co-ordinates. Protoviz tells me "Mercator" (http://vis.stanford.edu/protovis/ex/...
4
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5answers
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Converting LatLng coordinates to point shapefile

I have more than 50,000 LatLng coordinates defined under SWREFF99 1800 projection. I want to know, is it possible to convert these coordinates into a point shapefile ? if yes, then how can I do this ?
3
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2answers
1k views

Setting the map projection in the flex API to an overlay layer

I'd like to use a basemap containing world map data as a backdrop to some point and outline data that I'm hosting in ArcGIS server in the ESRI Flex API, but I would like the map control to share a ...
38
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6answers
20k views

Shapefile PRJ to PostGIS SRID lookup table?

I was wondering if there is such a thing as an shapefile PRJ to PostGIS SRID lookup table? Something that can translate the most standard shapefile PRJ definitions into the likely SRID. When using ...
7
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2answers
6k views

ogr2ogr srs options: where is the well known definition determined?

In the ogr2ogr documentation it says that when using -a_srs srs_def: Srs_def can be a full WKT definition (hard to escape properly), or a well known definition (ie. EPSG:4326) or a file with a WKT ...
0
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1answer
566 views

How to transform a DEM to a cartesian coordinate system?

I am using the script r.inund.fluv. I run the script with all the required parameters and it produced a lot or errors. I emailed the author of the script and he said that "I think you are not ...
11
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2answers
5k 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 ...
5
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1answer
401 views

Which projection casts rays from a point on the surface of the globe to a cylinder?

What is the name of a map projection that casts rays from a point on the surface of the globe to a cylinder? Some people who make sundials put a map of Earth on the sundial. I want to use the "right" ...
5
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1answer
2k views

Spatial Reference is null in ESRI Silverlight Map

I am using ESRI's Silverlight API to display a map with one dynamic layer. Occasionally (not always), when that layer is initialized, the SpatialReference attribute will be null. I'm not sure why ...
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2answers
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Extracting lat/long from screen when using British National Grid projection in ArcGIS Desktop?

Using ArcGIS Desktop 10.0, is it possible to click anywhere on the map (projected to British National Grid), but return the coordinates in WGS84 lat long?
4
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1answer
6k views

Convert a shapefile with northing/easting to ASCII raster with latitude/longitude

Linked below is a polygon shapefile whose projection is NAD83 and whose values are LU/LC codes. Coordinates are meters of northing and easting. I would like to convert it to an ASCII raster with ...
8
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3answers
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Bertin 1953 map projection settings

I am trying to use the Bertin 1953 map projection, as described in the book "Semiology of graphics" by Jacques Bertin. But I can't find the settings in any of my GIS software. Does anybody have a ...
5
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2answers
445 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 that ...
2
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3answers
937 views

MapServer - map rendered at the wrong angle

I've just started using MapServer to check the topology in my database, and whenever I render a map I have to flip the image vertically and then rotate it quite a bit to get it facing North. I've set ...
6
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1answer
3k views

Understanding why buffers not circular in QGIS?

I would like to select areas under a particular circular radius in QGIS. I believe this is accomplished with the buffer tool, but when I specify the radius the area is not circular. How to make them ...
52
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6answers
32k views

Why is the 'straight line' path across continent so curved?

This is the result of mapping the straight line path from a point in US to Poland using Distance Measurement Tool. Also, planes from Asia to US would travel almost over North Pole. Why is the path ...
4
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1answer
416 views

Using projections to obtain perspective views

I understand that a perspective view is essentially a type of projection. Is it possible to create projection definitions for a typical GIS system that will mimic a perspective view from a particular ...
3
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1answer
359 views

Two rasters created from the same polygon have different extents?

My problem is that I am trying to export some rasters to Rockworks so that I can create a sand layer from them. Rockworks requires the grid files i use to have the exact same XY co-ordinates. So i ...
16
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2answers
28k views

Converting projected geoTiff to WGS84 with GDAL and Python

Apologies if the following question is somewhat stupid, but I am only VERY new to this whole GIS thing. I am trying to convert some projected geoTiff images to WGS84 using gdal in python. I have ...
2
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0answers
609 views

OpenLayers WMS overlay tile projection

We are using OpenLayers for our GIS Application and we have base files from Ordinance Survey for UK maps. For creating WMS layers, we are generating tiles of 256 x 256 through Sharpmap Library but ...
2
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2answers
3k views

albers projection to Lat, Lon

Thanks in advance for helping me with my issue. This GIS stuff is using parts of my brain that have remained idle since high school, and some parts are working faster than others. I have land data ...
6
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1answer
7k views

Converting Lambert Conformal Conic to WGS84 using Proj.4

I am attempting to transform data from Lambert Conformal Conic lat/long and I am having some issues with the results. The shapefile I am attemtping to transform can be found here: http://tfr.faa.gov/...
2
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2answers
281 views

Why are results all black using gdalwarp via QGIS?

I'm trying to convert a bmp image in BNG to WGS84 using gdalwarp (via QGIS). It seems to be running without errors but the output is all black. What am I doing wrong?
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1answer
1k views

Reprojecting from MGRm to WGS84 using open-source tools

I would like to work with some of the Michigan state data (for example, this shapefile of cities ), but it is not in a common projection. However, when I try to reproject the file using ogr2ogr and ...
7
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1answer
961 views

Specifying PROJ.4 projection with North pointing down?

I would like to create a world map "upside down", with the South on top (in Mapnik). How can I achieve this? Can I take an existing projection string, e.g. Robinson projection, ESRI:54030. +proj=...
5
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2answers
1k views

How to set a map's extent to the envelope in miles

I want to set extent of the map into envelope which sizes are defined by user in miles(kilometers, whatever human readable unit). How to make it? I wrote the following code: static void ZoomToPoint(...
72
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5answers
39k views

Displaying coordinates and inputs as LatLon or LonLat?

I'm trying to get a sense if this is an issue for others or every input/output should be labeled so user is not confused and just go with it? I think almost everyone pronounces it as "LatLon". Who ...
8
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1answer
1k views

“On the fly” projection ON by default?

In QGIS 1.6, can users set "on the fly projection" to be checked ON by default (at application launch)? I know how to turn it on, but some users find they use it more often than not, and would like ...
3
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1answer
2k views

OpenLayers doesn't show an overlay with a different SRS than the base layer

I need to add an overlay layer that uses EPSG:4326 to a map with a base layer that uses EPSG:32628. Every time I add the overlay OpenLayers automatically switches the SRS param of the overlay to EPSG:...
8
votes
3answers
951 views

What kinds of line segments/edges require high accuracy in a true surface-of-the-ellipsoid representation?

I've been musing (and doing prototype coding) for a 'projection free' geographic codebase with your basic point, line & polygon primitives. Rather than dealing with all the sacrifices that come ...
5
votes
4answers
796 views

Given long, lat, x and y, how do I find the projection?

I am using an app called farsite that outputs shapefiles that show how forest fires will grow. I am getting output in coordinates as X and Y values rather than (lon,lat) and am looking for a ...
6
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2answers
12k views

Basic proj4 conversion UTM grid -> longlat and back

I'm a GIS novice, and am struggling to understand how to drive proj4 to accomplish what seems like a simple thing. I've googled for a couple of days, but everything I find seems to presuppose quite ...
10
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3answers
15k views

Understanding Coordinate System Transformation in ArcMap?

For the Data Frame Properties on a map in ArcMap, what is the difference between selecting a new coordinate system and using a Transformation?
11
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3answers
3k views

What is the right solution (and map projection) to compute distances between points located all over the World?

After my study on map projection I realized that it is very difficult to choose a projection that allows to compute simultaneously the distances between a great deal of points if these points are ...
8
votes
3answers
761 views

Global grid, which reference system to use?

I have seen a couple global studies using WGS84 as geographic reference, with the problem that the area of raster cells is not constant. Which reference system would you use for a global analysis in ...
8
votes
1answer
904 views

WGS72 to NAD83- how to find correct transformation

I am trying to get this raster file to convert from WGS72 to NAD83, but ArcMap10 doesn't appear to have the correct transformation listed. Where can I find this transformation, and/or how do I import ...
1
vote
2answers
651 views

How to add new projection using ArcObjects of ArcGIS for Desktop?

I want to use "Mars MOLA" { 86 3396000.0 3396000.0 "Mars MOLA" 0 0 0 0 0 0 0 } with my shapefiles.
5
votes
3answers
18k views

Using the Proj4js library to convert from Google Maps to projected values

I'm using the proj4s javascript library (based on advice from this question I asked previously) to convert lat/long values on my webpage. This page receives the lat/long values from google maps and ...
5
votes
3answers
1k views

FME - Possible to return a value from workspace?

I'm calling my workspace from the command line (either via Python or .NET to a system/os call). I'm parsing DWGs and pushing attributes to SQL Server in the workspace. Either the data validates in the ...
2
votes
2answers
3k views

Converting google map api coordinates into meters

How would I go about converting the results of my map bounding box into meters within javascript? For example, if I have the coordinates 51.52366625446907, -0.07467269897460938 decimal degrees, can I ...
8
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2answers
2k views

How do I rotate the OSM map before printing?

What is the simplest way to rotate and render Openstreetmap data, and still get a nice render? For example Toronto, would fit best rotated slightly on a page in landscape mode, so the northern ...
4
votes
1answer
578 views

No difference between distances measured in projected and non-projected data

I'm performing measurements of distances in Km between a lot of localities by using the "Point Distance" in ArcGis 9.3. I realized that the results obtained after using projected coordinate system are ...
31
votes
1answer
6k views

How to create an accurate Tissot Indicatrix?

A Tissot Indicatrix is useful method for communicating at a glance the kinds of distortion a given projection is prone to (in the figure below, each of the red circles occupies the same area). I've ...
6
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2answers
6k views

How should I use GDAL to perform a transformation?

I am a student who wishes to use GDAL to transform a series of images from Lambert Conformal Conic (EPSG: 9802) to Google Earth's WGS 84 (EPSG: 4326) for a web mapping project. I know that in order ...
29
votes
6answers
25k views

Defining projections for multiple shapefiles in ArcMap?

I have over 100 shape files that don't have .prj file and thus when I bring them into ArcMap 10 they show the coordinate system as unknown. I know all of the shape files coordinate system is GCS WGS ...
9
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4answers
1k views

World map projection with United States in center

I am creating a map showing flight paths originating in the United States and traveling to Asia and Europe. I need a projection for the world that will focus the United States in the center of the map,...
5
votes
1answer
2k views

Conversion of any projection to latlong using proj4 string

I am using a tool which uses proj4 lib to project maps. I have a set of xy coordinates to be converted to latlongs with that tool. as I have the source projection string say +proj=aea +datum=NAD83 +...
2
votes
2answers
637 views

Coordinate system in Map&Guide

One of my customers is evaluating transport planning software Map&Guide (http://www.mapandguide.com/) and what we require is to get the transport route data from their file to Garmin navigation ...
9
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6answers
3k views

Real-world example of Affine Transform?

From the Wikipedia article: In geometry, an affine transformation or affine map or an affinity (from the Latin, affinis, "connected with") between two vector spaces (strictly speaking, two affine ...
5
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1answer
3k views

Projected maps should but do not overlap in ArcMap? [duplicate]

I am very new to ArcGIS and trying to build a series of layers of data in ArcGIS 9.3.1 for a river catchment in Leicestershire, using data from several sources. All data covers at least the area of ...