A map projection is any method of representing the surface of a sphere or other three-dimensional body on a plane
1
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0answers
11 views
TileStache + Mapnik - Tiles are rendered randomly
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 ...
0
votes
1answer
66 views
GMT raster (*.tiff + *.pgw) in epsg4326 shifts few kms (4326-900913-3857 problem?)
This seems to be an old problem with an already known solution (ie. "...stop using 900913 and start using 3857..."), but not sure whether this problem is about software versions, the raster itself or ...
0
votes
1answer
21 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))
...
1
vote
1answer
39 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 ...
0
votes
2answers
24 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 ...
1
vote
1answer
21 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, ...
0
votes
1answer
88 views
Why do ArcGIS Area Calculations not match Official Statistics?
I am trying to calculate area of polygons using a shapefile from the world bank where countries are defined.
When however I am trying to calcuate the area, the numbers that emerge are different from ...
0
votes
0answers
37 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 ...
0
votes
0answers
26 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.
...
1
vote
1answer
19 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: ...
0
votes
4answers
159 views
Coordinates conversion doubt
In QGIS do I have a EPSG:4326 shapefile that shows the coordinates "-7148300 -3688500" and I need them in the format -64º -31º for further processing in a geodjango app.
However using ogrinfo I get ...
91
votes
9answers
17k views
What's the difference between a projection and a datum?
What's the difference between a projection and a datum?
1
vote
4answers
62 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 ...
0
votes
2answers
69 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 ...
5
votes
0answers
236 views
Evaluating map projection scale error
This is related to a previous question I posted. I am trying to quantitatively evaluate scale distortion associated with choosing different projection center, center azimuth, and scale factor values ...
1
vote
1answer
68 views
MMQGIS: How to make grid layer in meters not degrees?
I've read several of the posts on here pertaining to MMQGIS Create Grid Layer option, but I have not found information on how to make the grid based on meters veres degrees. I know how to manipulate ...
1
vote
2answers
47 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 ...
0
votes
2answers
44 views
Thiessen Polygons and Coordinate Projections
I am trying to perform a Thiessen Polygons analysis in ArcGIS 10.
My DEM is in GGRS_1987 and the point set I downloaded from Google Earth is in WGS_1984. The points display correctly but when I run ...
1
vote
1answer
53 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 ...
14
votes
1answer
779 views
How does one calculate distortion on Equirectangular Projection?
I am trying to calculate distortion so I can distort overlaying text and forms to precisely match an image of an equirectangular projection.
So, how does one calculate the distortion at a given ...
0
votes
1answer
60 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:
...
2
votes
1answer
80 views
Find projection of a point to a line
I have a segment defined by 2 LatLon points(A and B) and a third LatLon point (C).
I need an alghorithm, formulae, or some code to find the projection point of C on the segment AB (call this point D) ...
1
vote
1answer
57 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 ...
5
votes
3answers
2k views
Why don't my Shapefiles and OSM data overlap in Quantum GIS?
So I'm pretty new to GIS, and I'm working on a mapping project using data for Vancouver, Canada. I want to combine Open Street Map data along with data provided by the City of Vancouver. But the City ...
1
vote
1answer
26 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" ...
0
votes
1answer
48 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 ...
1
vote
1answer
36 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 ...
0
votes
0answers
32 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 ...
13
votes
6answers
4k 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 ...
0
votes
1answer
32 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 ...
2
votes
3answers
139 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 ...
1
vote
1answer
32 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, ...
2
votes
1answer
60 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 ...
17
votes
7answers
517 views
Spatial reference for dummies?
Can anyone recommend a good reference or tutorial that explains the principles of spatial references, projections, and coordinate systems? We are a small team of programmers working with GIS ...
11
votes
1answer
103 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, ...
1
vote
1answer
56 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 ...
1
vote
0answers
53 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:
...
0
votes
1answer
58 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 ...
3
votes
1answer
25 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 ...
8
votes
2answers
213 views
how to produce a Peirce quincuncial map?
As far as I know neither PROJ4 nor ESRI tools can apply the Peirce quincuncial projection.
Does anybody know what libraries/softwares can manage it?
1
vote
1answer
55 views
Why do points shift when reprojected from WGS84 to a state plane coordinate?
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 ...
2
votes
1answer
39 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?
1
vote
0answers
59 views
QGIS: Different projection result for on the fly and transformation
I am a bit confused about the result of a re-projection/transformation of a raster in QGIS 1.8 (Lisboa).
WGS84 to WGS84/UTM34N. When I use the 'on the fly' transformation the resulting raster has a ...
0
votes
0answers
19 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 ...
5
votes
3answers
229 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 ...
1
vote
2answers
48 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 ...
0
votes
0answers
24 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.
2
votes
1answer
157 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 ...
4
votes
2answers
219 views
Why isn't valid geometry not valid in NetTopologySuite when close to poles?
I have a Polygon which crosses the south pole:
Polygon in WKT:
POLYGON((5.86826073458095 75.6638564054071,-16.5436836399021 63.2220742891438,-19.3664667294083 59.846221066959,-21.7009816876343 ...
1
vote
1answer
49 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 ...
