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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234 views

Geotransformation for polar stereographic?

I'm currently working to import CANGRID climate data (provided as Surfer Grid ascii, ".grd" files) into ArcGIS. The grid is 95 rows by 125 columns in size.Metadata provides lat/lon of origin (lower ...
9
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756 views

How to define Winkel Tripel in proj 4.8.0?

I have QGIS with proj 4.8.0 installed. I'd like to add Winkel Tripel projection which seems to be defined as +proj=wintri But that definition string does not work. Is this a bug in my proj version, ...
5
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573 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 ...
3
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0answers
61 views

Why does field calculator compute area in square meters?

I am using EPSG:102748, and have set my Settings/Option preferred measurement units to ft. My CRS is NAD_1983_StatePlane_Washington_North_FIPS_4601_Feet, and when I use the measure tool, it returns ...
3
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0answers
39 views

Is there a way to expose Spherical Mercator Lat Lon in Google Map API?

The map tiles in the Google Maps are in Spherical Mercator projection (srid 900913), but in the API the methods report coordinates in Lat/Lon WGS84, e.g. map.getCenter(). Is there a way to return the ...
3
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0answers
125 views

Formula for maximum coverage of a geostationary satellite based on earth station elevation

I am trying to create a javascript function to represent the maximum coverage of a geo satellite for different antenna elevations (0 degrees, 5 and 10 degrees) with 3 leaflet polylines. The result is ...
3
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0answers
29 views

Distortion in projected raster

I am having a frustrating problem with something that I think should be very simple. I have a number of DEMs from the National Elevation Dataset (NED), that come standard in the NAD83 coordinate ...
3
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0answers
58 views

Is it possible to render tile-based web mapping projects in any other projection than web mercator?

Web-mapping technology has to a large degree adopted the web-mercator projection as the standard projection for displaying geographic objects with interactive map-clients. This is due to many factors ...
3
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306 views

Convert land-based camera image pixel x,y to ground lat/long or x,y,z

I have a number of cameras at various known locations (x,y,z) and directions that are above ground about 20 feet pointed at different ground locations about 100 feet away from each camera, and whose ...
3
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0answers
492 views

Fortifying re-projected shapefile for ggplot2 in R

I have a shapefile of US county boundaries which I got from the NHGIS. I can load the file using the rgdal package and see information about it: library(rgdal) shp_1860 <- readOGR("shp", ...
3
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46 views

Projection string for GOES-WEST

Full-res, full-disk GOES-WEST images are available from goes.gsfc.nasa.gov. Is it possible to rig up a projection string for these images? We know the center pixel is at (0N, 135W) and the satellite ...
3
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433 views

VBA Convert decimal degree to Meters button

I have 2 data frames one which has WGS data in it and the other OSGB1936. I am trying to create a button where the user can input decimal degrees (WGS) and it will zoom them to that location in ...
3
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462 views

Get tile URL with projection different than 900913

I have the following code, which should display a slippy map showing tiles producted by me with mapnik: Proj4js.defs["EPSG:31258"] = "+proj=tmerc +lat_0=0 +lon_0=13.33333333333333 +k=1 +x_0=450000 ...
3
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0answers
1k views

Converting projected coordinates to google maps pixels

I have a single polygon in a local projection system. I would like to convert that polygon into an image that can be used as an overlay on google maps. I understand that it may be better to use ...
2
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0answers
19 views

How can I get a web-hosted kmz file to project correctly when added as a layer to an arcgis online map?

I have a kmz file hosted on dropbox that I would like to display in a map through arcgis online. The kmz file was generated from an esri grid raster. I have tried altering the raster projection prior ...
2
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0answers
124 views

Working with AIG Raster format in ArcGIS for Desktop?

I downloaded a specific layer which has the format "AIG" as you can see in the screenshot. It has no projection so I applied "Define Projection" on it. I searched for the projection and found the ...
2
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39 views

QGIS CRS correct, but layers appear warped

I am trying to overlay a raster Landsat 8 scene and vector scene boundary. Both are using WGS 84 + UTM48N. However, the vector (orange line) appears offset when overlaid on the raster. I have checked ...
2
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51 views

Mine Grid to UTM

I have been given spatial data (lidar) that was collected in mine grid feet in ASCII format. I am using arc to process but need to define a projection does anyone know how to do this or any other ...
2
votes
0answers
32 views

Project lines onto surface in QGIS

This question may already be answered so please point me in the right direction. I am designing a water distribution system for a rural village in Guatemala. I have created contours for the area. I ...
2
votes
0answers
58 views

How do you clip a gnomonic or stereographic azimuthal projection?

I have polygons comprised of lat/lon coordinates and I want to project them onto a plane that's appropriate for polygon operations (such as checking for intersections). In some cases, the polygons ...
2
votes
0answers
326 views

ArcGIS WGS84 Web Mercator Vs. WGS84 UTM zone 15N: Very different distance dimensions

I am working in ArgGIS 10.1 with a field (raster layer in tif format) in which I have placed two points (.shp layer). I have two versions of both layers, resulting four layers: one tif+shp set in CRS ...
2
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0answers
126 views

Difference between feature to raster and polygon to raster

(I'm using Arc 10.1) I'm trying to rasterize a data set. I have a shapefile with geographic coordinates (GCS_GDA_1994) which I want to convert to a raster with 100m grid cells. So I need to project ...
2
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0answers
40 views

Is it safe to store coordinates on NFC tags always in one CRS and rely on conversion for others

I'm involved in NFC (Near Field Communication) standardization of a record structure for geographic point locations. That will allow to put coordinates on NFC memory tags which can be read with a ...
2
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0answers
125 views

How can I improve the resolution of a vector grid made in north pole stereographic projection?

I've been struggling with this for a while and wondered if someone could lend a hand. I have a map which already has sampling points from centroids in a 35x35km grid that was created in north pole ...
2
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0answers
37 views

Differences between points and lines as poles in an equal area projection

I am planning on using an equal area projection in a current project. I used this website to determine which projection I should be using. I hadn't previously considered it, and was wondering if ...
2
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0answers
1k views

How do I change from lat/long to a metric coordinate system in GRASS?

Yes, it's yet another transformation question. I am working with ASTER DEM data, which is LatLong WGS84. I want to process the DEM map into an STL file for use in a CFD simulation. The script I am ...
2
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0answers
671 views

Projecting a Raster from WGS84 to planar Equal Area to Calculate Area: How to Select the Cell Size?

I have a broad question on how to calculate the 'correct' cell size for a raster when analyzing an area not at the equator. My goal is to project a land cover raster provided in GCS WGS84 to an equal ...
2
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0answers
150 views

Proj4 inconsistent longitude after projection

All coordinates expressed in this question are (longitude, latitude), the default for proj4. London is at (-0.1460838, 51.5170986), and San Francisco is at (-122.419302, 37.775549). According to the ...
2
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0answers
184 views

Mercator projection that shrinks toward pole

I've noticed that lots of map viewer (especially those nautical chart viewer) will shrink a mercator projected chart while panning towards poles. Is this some compensation for mercator distortion? ...
2
votes
0answers
328 views

Mapserver+openlayers: displaying a shapefile with Cylindrical Equal Area (Lambert) projection

I have some shapefiles in "World Cylindrical Equal Area (Lambert) projection". The .prj reads: PROJCS["World_Cylindrical_Equal_Area",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_ ...
2
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0answers
183 views

projection discrepancy with gdal (1.9) and proj4

I boiled the problem down to that python example: import sys try: from osgeo import gdal from osgeo import osr except: import gdal import osr if __name__ == '__main__': version_num = ...
2
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0answers
131 views

Projection declaration in dojox.geo.openlayers possible?

I am trying to integrate some maps of my own into the dojox charting demo and I had success in exporting a shapefile (externally, i.e. with my own parser) to the dojo JSON map format. The map is in ...
2
votes
0answers
87 views

Recommendations on universal projection API or algorithm for ArcObjects?

As asked on the esri forum here, we are trying to convert a geometry from any spatial reference to any other spatial reference. We have tried the default IGeometry.Project(target_spatial_reference) ...
2
votes
0answers
504 views

Help converting projection/coordinates to Google Earth

I'm trying to program a GPS style tracker for a simulation game but I'm having a hard time figuring out how to transform the game's coordinates into Google Earth's. The game's world is flat and has ...
2
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0answers
100 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 ...
2
votes
0answers
492 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 ...
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0answers
18 views

QGIS - Label polygon with different projections

I have a polygon layer projected in an UTM. In properties I checked 'show all labels for this layer'. Does anyone know why the label does not show until zoom 15:1 in QGIS with CRS-4326, while in ...
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0answers
28 views

Unknown coordinates in Shapefile, projecting doesn't give expected results

I'm reading a Shape file (four files actually, .dbf, .prj, .shp and .shx) containing polygons representing certain areas in my neighborhood. For this I use C# and a library called DotSpatial. I can ...
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0answers
53 views

Length difference between Google Earth and ArcGIS for Desktop?

I have drawn a complex path with multiple vertices in Google Earth (GE) Pro and its measurement property is shown as being 2,460 nm. It is located East of Australia. If i import this KML into ArcGIS ...
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0answers
25 views

Resampling methodology when projecting a raster

When projecting an SRTM raster with "Project Raster" tool in ArcGIS10.2, what is the best resampling methodology, bilinear ot cubic convolution?
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20 views

QGIS (2.0.1): Field calculator for length not working - values way too high

Same problem as another thread: Field Calculator returning incorrect length and area values Trying to calculate length of a line shapefile, and field calculator is returning values that are way too ...
1
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0answers
80 views

Show a kml (which uses longitude and latitude EPSG:4326) in “google/OSM” projection (EPSG:3857) in open street map

I am showing a kml layer, over OSM. The points in the kml are latitude/longitude (EPSG:4326). I don't have to convert any points or anything, it all just works. Great! Now, the client also wants to ...
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0answers
39 views

Projection problems when importing .kml from Google Earth to QGIS

I want to open several points that I exported from Google Earth as a .kml in QGIS for further use. I can import the data and the points are displayed but something must be wrong with the projection as ...
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0answers
48 views

How i can have the same xMin,yMin for vector files in Qgis 2.4

i have a .shp file(polygon) in EPSG:2100 - GGRS87 / Greek Grid and an other .shp(points) in the same system(EPSG:2100 - GGRS87 ) but different xMin,yMin. The first has xMin,yMin 583309.00,4152885.94 ...
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111 views

How to prevent cross-world lines in ggplot world map?

I'm having issues displaying 'great circles' paths and polygons in ggmap, an extension of ggplot2. Please enter the following code to replicate my issues: ...
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0answers
27 views

Can I get Geoserver to return a WMS in gnomonic projection?

I need to be able to pass in the center lat and long. I have tried using the AUTO Namespace for SRS (which works) but this only supports a few projections, the closest being orthographic. I have ...
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0answers
40 views

Appropriate reference system for small-scale mapping of the Middle East

I want to create a thematic map of the Middle East that displays certain historic places and regions on a small-scale map (between 1:6.000.0000 and 1:12.000.000). The map has to center the boundary ...
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0answers
61 views

Clustering the WGS84 point features (projection transformation aspects)

My question is quite trivial and was discussed many times before (like here) but in our case it has the confounding extra requirements... The list of sparsely distributed 2d point features is stored ...
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0answers
24 views

Projecting Data with Transformations - Alignment Issue

Problem: I am having problems getting data to align properly with basemaps layers. The image below shows the difference between roads. The centerlines shapefile's coordinate system is ...
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0answers
304 views

How to overlay a flat image onto google maps with two points of reference?

The Android API allows for images to be superimposed onto a map. To do so, the developer specifies a set of lat/long coordinates for an "anchor point" within the image, the width (or height) of the ...