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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How to correctly specify coordinate system?

Using QGIS v. 1.9 (1.7 does not seem to be available for Ubuntu Linux 12.04), do the following: Create new project, specify coordinate system by clicking on button in bottom right hand corner, ...
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2answers
490 views

How do you change the prime meridian of a map?

I am working with the Natural Earth world map as a SHP file, but when I try to change the prime meridian (PRIMEM) of the coordinate system ...
3
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1answer
961 views

What is wrong with this Proj4 transformation?

I'm implementing support for WMS maps in my company's software. Servers return a list of projections their maps are available in, but our software only displays data in WGS84 (lat/lon or UTM), and ...
4
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1answer
254 views

Automate database conversion from NAD83 to Web Mercator

A NAD83 database is updated daily while a Web Mercator clone is only update when time is available. Looking to automate this process of Copying Layers Projecting them to Web Mercator Placing in ...
5
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2answers
4k views

How do I get the distance meter value between two geometries in PostGIS?

I have a simple question about calculating distances in PostGIS. I would like to get the distance between two geometries. I am using this sid : 4269 in meters what i am doing now is this : ...
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464 views

How do I use Proj4js or other technique to make custom map projections with google.maps.Projection?

I'm using Google's Projection class to try to convert my map projection from the default spherical mercator to something like Lambert Conformal Conic. I was previously adapting the code from this ...
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3answers
6k views

How do I include proj4js in openlayers?

in my Openlayers app, since the base map projection is not epsg900913 or 4326, I need to include proj4js in order to use geolocation feature. but i got such a error notice: GET ...
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2answers
434 views

How do I determine the projection of a paper map?

If I'm reading a paper map how do I determine what projection was used to draw the map if such information is not explicitly labelled on the document? Online it is easy to find resources (for ...
4
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1answer
321 views

Projecting gps data to get length of resulting line shape in ArcMap 10.0

I have gps data in WGS84 geographic coordinates. I will use the gps data to build a line shape in ArcMap 10.0. The data falls in UTM 15N. To get most accurate length of line, should I project the ...
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0answers
152 views

How to show an array of 2d points/polygons in Polymaps (Cartesian coordinate system)

I need to display these 2d points/polygons (Cartesian coordinate system) on Polymaps with GeoJson layer. I do not use the other layers. Do I need to convert xy coordinates to the lat lon? If so, how? ...
2
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1answer
4k views

How to convert decimal degrees units to km in R?

I am trying to figure out how I can transform my unit of length from decimal degree to km when I import the following simple ArcGIS polygon shape. Ultimately, I would like to have this information ...
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0answers
63 views

What projection is this [duplicate]

Possible Duplicate: QGIS - Hell of time with CRS and vector intersect The tax assessor parcels layer I referred to in my first post gives this as its projection: +proj=lcc ...
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2answers
1k views

Image tiling math

I've been looking at MapTiler for the logic on how to render an image as tiles on a (google) map. Instead of storing the single tiles locally in a folder structure I want to use Djatoka. I'm able to ...
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0answers
607 views

Geoserver tiles mismatch

I tried to get WMS tiles from geoserver like /geoserver/gwc/service/tms/1.0.0/layername@EPSG%3A4326@png/15/19142/9530.png or with another projection ...
3
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1answer
471 views
2
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0answers
105 views

raster data expressed as percent

I downloaded NDVI greeness data from the USGS Integrated Vegetation Mapping Viewer. In the metadata it says that visual greenness values range from 0 to 100. My data is from the period ending 3/5/12 ...
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2answers
382 views

Geowebcache re-projection

I have one layer (raster geotiff image) published in geoserver with EPSG: 3011 projection. But I want this layer in EPSG 4326 projection for use it in google API web application. I have searched on ...
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2answers
106 views

Need Image with Sweref99_1800 projection/coordinate system

I need third party image tiles (probably world imagery) under sweref99_1800 projection and coordinate system (EPSG 3008). I found this link ...
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2answers
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How is EPSG:4326 data 'projected' in a 2D map?

I like to think I'm relatively well-versed in datums, projections, and coordinate reference systems, so if this is a stupid question I will suffer eternal shame. OpenStreetMap data is stored in WGS84 ...
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2answers
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Which world map projection allows comparing countries by shape and size?

The Mercator projection increases scale along with the latitude. Greenland seems larger than Australia, when in fact it is much smaller. The equal-area projections however stretch shapes away from the ...
12
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1answer
628 views

How is a “conformal latitude” used in ellipsoidal stereographic projections?

At my work, I've been doing some maintenance on internal software that claims to implement a Stereographic projection whose formulas were copied from an old system a long time ago. From what I've ...
5
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1answer
3k views

Mercator projection: problem with latitude formula

I'm trying to get the position of a coordinate on this map (source Wikipedia): If I'm correct than the formula for the position of the latitude would be: R * ln(tan(pi/4 + latitude / 2)) But ...
22
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1answer
7k 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
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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?
2
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1answer
605 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 ...
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5answers
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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 ...
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7answers
434 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 ...
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1answer
684 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 ...
3
votes
1answer
1k 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: ...
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834 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 ...
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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
624 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 ...
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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
190 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
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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
622 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 ...
3
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2answers
181 views

Can you search WMS services for a particular projection?

Is there an interface or website to search public WMS services for location/projection?
3
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2answers
534 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): ...
2
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1answer
133 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
532 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
237 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 ...
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2answers
2k 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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vote
1answer
655 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
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4answers
3k 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
8k 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
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1answer
389 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 ...
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3answers
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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 ...