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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568 views

TileStache + OpenLayers TMS - Tiles are rendered disorderly

I newly turned to TileStache to render Mapnik tiles because of the caching option. Before, I was using Mapnik python bindings only and it was working perfectly. Now that I use TileStache, the tiles ...
2
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2answers
1k views

OGR Projection transformation error

I am trying to convert shapefile that was created by FME in EPSG:900913 to EPSG:3857 (I know its the same definition) with OGR in a script. datasource = ogr.Open(os.path.join(dirname,shapefileName)) ...
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1answer
2k views

How to transform World data from EPSG 4326 to EPSG 3857

I have tryed different opensource tools to transform a world data shapefile from 4326 to 3857 but I always have an error. Im not sure, but is it because of Antartica? I have tryed with GDAL and QGIS ...
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2answers
604 views

How to scale/reduce my polygon without changing the central lat & long?

I am writing a VBA code to resize my polygon, I get a input as vector points(Shape file). The code below resizes it as according to my scale factor but my central latitude and longitude are also ...
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183 views

How to find out what projection my data is using?

I have a set of data that I created from gps locations of images. The locations are in decimal. I don't know what projection was used when the data was captured. I used QGIS to display the data with a ...
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1answer
276 views

Pseudo Mercator error?

I'm mapping on QGIS, I have a vector layer and his CRS is on EPSG:4326 - WGS 84, but also I wanted to put a satellite image, so when I do it, the image use WGS 84 / Pseudo Mercator. The problem is, ...
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0answers
98 views

need info on GeoTIFF projection keys

I am a programmer (not a cartographer!!) developing an application which needs to read and write GeoTIFF files. I have a number of questions about those GeoTIFF keys which are related to projections. ...
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1answer
53 views

Editor and projections ArcGIS

When opening an edit session Arc is telling me that some of my shape files' coordinate systems do not match the data frame. Here is the data frame coordinate system: Stereo_70 Projection: ...
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2answers
105 views

Digitized Shapefile manually using wrong projection: how to fix it?

I have a raster in correct projection. I used shapefiles, and marked objects (manually), but I found out that my vector layers have different projection, so they have different size and position. Is ...
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4answers
620 views

What projection to use in ArcMap for a map that extends over Wgs84 Utm31 and 32

Please i have a Wgs84 Utm map that extends over 2 utm zones(31N and 32N). Using either of them distorts my map and ArcGIs allows you to choose only one projection per map. Please what can i do? Thank ...
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2answers
188 views

Mapping elements in a warehouse

I am new to GIS. For a small project I want to map elements in a warehouse and want to find the location of the elements later (e.g. nails are located at x,y). Now I am wondering what kind of ...
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1answer
524 views

How to create a Winkel-Tripel map of countries with different colors?

I need a good quality rasterized world map, Winkel-Tripel projection, in which all countries have different (random?) colors. No borders, text, grid or anything else on the map. Is GIS the right way ...
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1answer
208 views

If I've given two different layers the same CRS, why won't they overlay one another?

I have a "towns" and "state" shapefile for Massachusetts as two separate vector layers in QGIS. I've set the project coordinate system to WGS 84 at the bottom of the screen (next to the "coordinate" ...
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1answer
325 views

Why does map display like it is in Isometric when everything is in EPSG:4326?

I'm beginning with Geoserver and try to display a map of my country (Belgium) is an openlayer map (embedded into a MapPanel object). I've downloaded the municipalities limits from gadm.org and copied ...
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1answer
78 views

Some terms related to coordinate

I was googling coordinate related information all the day. Now I am confused with some concepts and terms. I hope some one can help me to make it clear. Geographic coordinate system Geographic ...
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1answer
72 views

When is a projected length calculated via a pythagorean distance more accurate than an ellipsoidal length?

I'm using spatialite 3.0.1 with the following test data (in EPSG: 4326): Name astext(geometry) ---------- -------------------- Belitsa POINT(23.563 41.947) Malko Tarn POINT(27.533 ...
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0answers
41 views

what is the difference between the Geographic coordinate, transformed coordinate and screen coordinate [duplicate]

What is the difference between the Geographic coordinate, transformed coordinate(projected) ,cartesian coordinate, and screen coordinate? Is there a live example? And what is the association between ...
2
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1answer
140 views

Wrong object size after projecting spatial data from one coordinate system to another

I am having problems reprojecting items in ArcMap 10.1 from British National Grid To WGS84. (WKID: 27700 Authority: EPSG to WKID: 102100 Authority: ESRI) All Polygon Layers I project [I use Project ...
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3answers
5k views

Which CRS to use for Google Maps?

I am trying to map a Shapefile (download) onto a Google Map using the Javascript API. The Shapefile describes the boundaries of NYC School Districts. The file's projection was Lambert Conformal ...
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2answers
100 views

Is it possible to have another CRS in the status bar than used for the map?

I am new to QGIS. When I use OSM or Google Maps as a basemap via Open Layer Plugin, the map should be projected as EPSG: 900913. However, the Coordinates shown in the status bar are useless for me, ...
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2answers
779 views

Tile script (Mapnik) with OpenLayers - Problem with projection (900913)

I use Mapnik python bindings in a geodjango application to render tiles in openlayers with datasource stored in postGIS in 900913 projection. The feature seems to be rendered correctly in the ...
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1answer
527 views

Blank MapServer WMS image at low zoom levels in OpenLayers

I have an OpenLayers map using OSM as the baselayer with several layers coming from MapServer via WMS. The OL map is in EPSG:3857 and my mapfile (and shapefiles) are in EPSG:4326. In my mapfile I ...
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1answer
537 views

how to make the translation between latitude/longitude and screen pixels

The earth is three dimension object while our screen is two-dimension. So when we use the gis software to display the geographic data, how do they handle the translation between latitude/longitude ...
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0answers
611 views

Using gdal to convert from UTM to equidistant lat/lon

I am getting rather confused with converting a UTM gridded dataset into a equidistant/rectangular latlon gridded dataset. Can anybody help me? I have a UTM set with the following projection: ...
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1answer
516 views

Problem Overlaying layers in OpenLayers

I have a html page with 2 WMS layers. The first is one Base Layer , & the second is my personal WMS feature. I load it from Geoserver. The problem when I add the 2 layers I do not have the ...
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1answer
46 views

Does IDistanceOP.EucDistanceFull require a projected coordinate system?

I have designed an implementation of ArcObjects' IDistanceOP.EucDistanceFull. It takes its input as a feature class and converts it to a GeoDataset with which EucDistanceFull can work with. It works ...
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1answer
301 views

Why do points shift when reprojected from WGS84 to a state plane coordinate? [closed]

We have a Trimble unit we use to collect equipment. We collect the data in WGS84 and differentially correct it and then reproject it to a state plan coordinate system. The points always shift the ...
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20 views

De facto QGIS projection for EPSG4326 / 'unprojected' reference systems? [duplicate]

This is my understanding of projections/datums: To get a map of the earth on a plane you need to project the 3 dimensional earth by 'wrapping' a plane around it in the way that suits you (according ...
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1answer
160 views

Do FeatureLayers reproject their features to adapt them to the map projection?

I'm working with the ArcGIS Flex API. For example, ArcGISDynamicMapLayers do reproject their data in order to make it in the same projection as the map. Do FeatureLayers have the same behaviour?
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31 views

QGIS: Unable to project raster layers correctly on a Toshiba Tecra 64# Win7

I know how to project a raster, I can do it on other machines. On this particular machine the raster loads but are no where near the correct position as if the datum is on another planet.
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358 views

Assign projection to a satellite image

Today I stumbled upon a picture taken from the ISS looking down Europe and it is really beautiful. So, I started thinking I could add more to the picture. Like world borders, cities, road network, ...
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2answers
309 views

define a datum and meridian in a CRS in QGIS

I have a shapefile defined by the source as: "The layer is in geographical (lat-long) coordinates (GCS_Clarke_1866; Datum: D_Clarke_1866; Prime Meridian: 0)." opening the shapefile in QGIS 1.8 the ...
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1answer
325 views

Incorrectly Projected PostGIS data in TileMill

When I bring PostGIS data in EPSG:900913 into TileMill, my layers end up on other continents. This is my workflow: (1) Save shapefiles in QGIS to EPSG:900913 (2) Import the shapefiles using PostGIS ...
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1answer
577 views

Wrong projection on WFS layer with OSM baselayer [duplicate]

I am trying to add a vector layer with a WFS protocol. var wfs = new OpenLayers.Layer.Vector("WFS", { strategies: [new OpenLayers.Strategy.BBOX({resFactor: 1})], ...
2
votes
1answer
3k views

What are the units of the calculated area from a raster in decimal degree

I'm trying to calculate area for a raster file which contains 2 layers (0 for unsuitable habitat and 1 for suitable). It's been calculated successfully but I don't know what is the unit of the ...
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0answers
55 views

how to get correct geo reference system for a VMap

I am new to GIS, trying to read the GeoRef System for VMap by using the following code: OGRSpatialReference *ref = layer->GetSpatialRef(); if( ref ) { QString georefSystem = ...
14
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2answers
2k views

What is the approximate error of the Pythagorean Theorem vs. Haversine Formula in measuring distances on a sphere at various scales?

Many people when first trying to calculate distances between two longitude / latitude pairs ask if Pythagorean theorem works as an appropriate distance function. Most often people answer "no, the ...
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0answers
105 views

How to get Earth radius in pixels?

I need Earth radius in pixels for use in Mercator projection. Well let's say that our map's height is 1478 pixels and distance between 0 pixel and 1478 pixel is 2.52 degree. Radius is distance from ...
3
votes
1answer
162 views

Compute global DEM topographic indices and compromise projections

I would like to compute global topographic indices based on SRTM elevation data. These indices are computed along river/channel networks extracted from a DEM and are a functions of both local slope ...
1
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1answer
1k views

openlayers multiple layers with different projection

My page contains two layers: 1. Open Street Map as a basic layer and WMS layer from mapserver as a overlay layer. My map show this two layers but in a wrong position. I spent a lot of time trying ...
3
votes
1answer
84 views

What is displayed when I am using a geographic CRS for my project

I understand that each geographical dataset has a CRS, and that in order to overlay them, you need to either make sure that all datasets use the same CRS, or re-project some of them (or use on-the-fly ...
7
votes
2answers
332 views

Should point data be equidistant projected when using ArcGIS IDW spatial interpolation?

I am wondering if anyone can clarify whether point data should be projected to an equidistant projection when using ArcGIS IDW spatial interpolation? I am working on a dataset from Western North ...
0
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2answers
556 views

OpenLayers WMS - TypeError: this.resolutions is undefined

I'm trying to setup a map with WMS and WFS Layers by using Geoserver. However, when I'm combining WFS and WMS (with some Google basemaps) together in one map I got following error in Firebug: ...
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0answers
150 views

I want to change EPSG:4326 to EPSG:900913 using C# for a set of uploaded shapefiles

I have written some code (using help from these pages) that uploads a directory full of shapefiles to a geoserver using C#. The uploaded shapefiles are set to EPSG:4326 however I would like them to be ...
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0answers
231 views

Reprojecting raster data from a rotated pole grid

I have some raster data (ASCII grid files) that use a custom rotated-pole projection, that I'd like to reproject into something more useful, such as lon/lat WGS84. A description of the grid projection ...
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2answers
632 views

WFS reprojection problems

In geoserver i have a layer in EPSG:4326. In OpenLayers i add it on map as WFS: markerLayer = new OpenLayers.Layer.Vector('Markers',{ strategies: [new OpenLayers.Strategy.BBOX()], ...
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1answer
300 views

How to Extract Data from U.S. National Landcover Dataset (NLCD) dataset?

I am working with U.S. National Landcover Dataset (NLCD) to classify habitat type at more than 150 sites across the northeast U.S. The dataset is very large (15GB) so I cannot upload it here, but it ...
0
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1answer
97 views

Imported GPS data does not overlap with map

I´m working on QGIS and I geocoded 2 addresses of a city in Germany and tried to input the text-file as a layer. It worked, but the 2 points must be in the map of the city and if I zoom to the ...
2
votes
1answer
403 views

Transformation of user-defined projected coordinatesystems

I want to transform from one projected coordinate system (pcs) to another using ArcGIS 10. Unfortunatelly the starting system is not predefind by ESRI and thus I´m not sure the software is doing what ...
2
votes
1answer
92 views

Ok to measure and union a projected-on-the-fly shapefile in ArcMap?

I have a dataframe in arcMap 10.0.4 that is of Africa Albers Equal Area Conic PCS. I bring in a census shapefile of WGS 1984 CS and it is projected on the fly. I do 2 things: I use the calculate ...