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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764 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 ...
4
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55 views

How to choose the EPSG projection?

Up until now for reprojection of my WGS84 vector (.shp) and raster files (.tif), I have been using EPSG projections based on vector/raster central point's UTM zone. But what happens if the ...
4
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0answers
60 views

The drawing of Thiessen/Voronoi polygon boundaries - are the bisecting lines truly perpendicular?

I am concerned with how QGIS (version 2.8.1) and ArcGIS (version 10.0) draw "perpendicular bisecting lines" when Thiessen/Voronoi polygons are created. When using either program to create these ...
4
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0answers
545 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 ...
4
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0answers
235 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 ...
3
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29 views

Rectangle shapefiles with the same extents does not align perfectly after projection

I have a rectangle shapefile built with UTM19 coordinates using a python script, and then projected to NAD83_CSRS (EPSG:4617). I have a second rectangle shapefile built with the same method (python ...
3
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37 views

GDAL c# API returned different WKT from gdalinfo

I've found completely different results in WKT strings while using gdalinfo utility and method from c# API GetProjectionRef(). In the first case the result was: PROJCS["WGS 84 / Pseudo-Mercator", ...
3
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67 views

How to calculate false easting/northing for Lambert Conformal Conic projection

I'm defining a new GRASS location using the Lambert Conformal Conic projection. My understanding is that the values for the standard parallels and central meridian are dependent on my area of ...
3
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48 views

Transforming lat and long to Mercator x and y

I've been trying to plot a set of lat and long coordinates to a Mercator map using the following set of equations; x = long - long0 y = ln(tan(pi/4 + lat/2)) These equations are from a page on ...
3
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52 views

Wrong area using Albers Equal Area Projection in GRASS for Java, Indonesia

I am just getting to know GRASS 7.0 and I am struggling finding a good projection to work on a spatial analysis of Java, Indonesia. I am new to the forum, so if information's are missing for a better ...
3
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0answers
50 views

Do locations “move” when shifting datum?

I hope that this is the right Stack Exchange for this question. I may be oversimplifying this, but I'm looking for verification in my understanding of the following: If I have a spatial dataset in 2 ...
3
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0answers
97 views

Which projection can I use to see alignments on great circles?

I want to put on a QGIS map some historical sites to check if they are aligned. If an alignement exists, the points should stay on a great circle (is this correct?). I want to visually verify this ...
3
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0answers
312 views

Align vector and raster layers with D3

I have a geocoded raster image that I want to use as the background to a vector map with D3.js. The screenshot shows the layers in QGIS (grey is raster). Here's the markup for the map: <div ...
3
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0answers
76 views

Finding centroids for icosahedral gnomonic projection?

I've been trying to create an icosahedral gnomonic projection, like this example by Jason Davies or this one (the Fisher projection). The method that I initially used was using the centroid of each ...
3
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0answers
294 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
203 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
345 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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71 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
85 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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0answers
828 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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0answers
59 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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0answers
597 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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0answers
640 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
35 views

Calculate Geometry function returns underestimated distances

I'm making a map of the Colorado Trail and obtained a set of waypoints taken down the entire trail. I projected the set of waypoints from WGS84 (unprojected) to NAD 83 UTM13N after adding to the data ...
2
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28 views

Visualizing netCDF file with unknown projection

I'm having a tough time visualizing a netCDF file with poor metadata in ArcMap, which is probably not a surprise. I know the file to contain ozone concentrations over the United States. If I try to ...
2
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0answers
26 views

Problems with matching vector data with raster data

I’m new in Arcgis, and I have some trouble in this task: I downloaded from ICC (www.icc.cat) a raster data map that is a in a specific coordinate system, if I right click to view its properties, it ...
2
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0answers
41 views

Converting from unknown coordinate system into common one using fiducial points?

I have a thousand of points that I want to project in a different coordinate system. These points were generated using an old and odd coordinate system (let's call it CS) so it's not possible to use ...
2
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0answers
29 views

Converting u and v from WGS84 to NZTM2000 - Do I need to do vector conversion?

I have u and v wind component values in latitude and longitude in WGS84. I want to convert this to NZTM2000. I've converted the lat/lon in ArcView - (and will try in R) - but do I need to also do some ...
2
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0answers
24 views

OpenLayers measurment path in 31700 projection

I have this code who works great for distance measurment on 900913 projection with 4326 display projection (bing maps + layer WMS): measureDistanceControl = new OpenLayers.Control.Measure( ...
2
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0answers
41 views

How can I move a polygon to a different place on the globe, while maintaining its true geographical size? (QGIS)

I'm trying to do something similar to the Greenland vs Africa comparison -- superimpose one country over another, showing how their true sizes compare (the example on the right). Thought this would ...
2
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0answers
54 views

Changing projection on each page of data driven pages

I am working with data driven pages and a raster image of the world. I have a separate polygon shapefile of all of the UTM zones (with a polygon for zones 1-60, north and south, for a total of 120 ...
2
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0answers
86 views

Converting from flat earth to WGS84 with python

I'm looking to move from basic 2d Cartesian coordinate system into WGS84. I know my starting coordinates, however all intermediate points are x/y/z points. of an origin 0,0,0 . Mathlab has a ...
2
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0answers
38 views

Aligning Points in Decimal Degrees

Running ArcMap 10.3 I am displaying a layer of manholes from a table coming from SQL. The XYs are in decimal degrees however they are displaying no where near my other layers (NYC PLUTO). I have ...
2
votes
0answers
62 views

Thiessen polygons extend outside of extent of projection

I'm working on a geological project on the past position of continents (in ArcMap 10 Service Pack 5, build 4400). The tool I'm creating in Model Builder uses Create Thiessen Polygons and all input ...
2
votes
0answers
132 views

set Default projection in postgis table

I've set the SRID 4326 for a table having geometry column, but when i insert a geometry without SRID, i get an error because no SRID specified is interpreted as -1 or 0, so how i can set a default ...
2
votes
0answers
86 views

Reverse parameters of a projection map

I'm user of a soaring simulator named "Condor Soaring". This simulator is at the center of a community of enthusiastic people who build sceneries (landscapes) which represents quite accurately real ...
2
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0answers
85 views

ESRI/Mapinfo MGA56 prj vs QGIS MGA56 prj

I am trying to understand why the degree unit is different between ESRI/Mapinfo and QGIS: ESRI/Mapinfo ...
2
votes
0answers
110 views

Stretching of geometry when rasterizing vector data on Google Maps

I'll start with a quick backstory on what I am trying to achieve. I'm working on an offline Android GIS tool and people are throwing giant datasets at it. It converts these into Google features (V2) ...
2
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0answers
38 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
493 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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0answers
333 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: ...
2
votes
0answers
91 views

Reprojecting PostgreSQL/PostGIS data as it streams in?

I have a postgres/postgis database. I would like to reproject those data coming to me in 4326 to 32736. For those tables with lat long info in wgs84 (4326) I have set the geom to 4326. Then I have ...
2
votes
0answers
67 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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0answers
135 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
46 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
131 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
249 views

MySQL+GDal+MapServer+OpenLayers WebMercator problem

I have a problem/question what is the most efficiant way to go from WGS84 (epsg:4326) to webmercator. Outline of the structure right now: MySQL Database: with point Latitude/Lontiude Data [~200 ...
2
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0answers
66 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
164 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 ...