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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Convert an arbitrary meta-data-free map image into QGIS project

My background: experienced programmer, amateur historian, complete beginner to GIS (so I'm using QGIS). I did learn to use the QGIS georeferencer tool though. The input: suppose I have an image like ...
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4k views

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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1answer
613 views

Equal Area SRID for Australia

Does anyone know the SRID for an equal area projection that is suitable for the whole of Australia? I realize that I could make my own (which I have done) but I am looking for one that is present ...
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3k views

what is the best way to programmatically convert between WKT and Proj4 string?

some shapefiles have a .prj file associated with it. and the .prj file contains the projection info of the shapefile in the format of WKT. Sometimes I need to convert WKT to proj4 string, and ...
7
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278 views

Sentinel-2 projection shift

I recently observe a shift in the geographic projection of Sentinel 2 data. Please see the screenshots below for clarification (Granule T33UXP, Band 8 only). The first image was taken on 20160314, the ...
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353 views

Can I just swap out a .prj file to reproject a shape file?

I'm an experienced software developer -- but a GIS noob. I have a shape file that I am trying to turn into a SVG map with Kartograph. When I try to run Kartograph I get this error: ERROR 6: No ...
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482 views

Method to generate points in any projection

I am writing an application in ArcMap to generate a grid of points. These points have a very defined layout and I have worked out an algorithm that works great under a projected coordinate system. ...
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1answer
4k views

What's up with the GeoJSON spec and CRS as a IRM?

I'm writing a web API to our GIS data, currently revamping our geocoding service. I'm creating the option for folks to specify the output type as GeoJSON so I'm trying to follow the spec. Our data is ...
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254 views

Understanding difference between Coordinate System and Projection?

Can somebody please explain what is the difference between the Coordinate system (WGS 84 for example) and a Projection (Universal Transverse Mercator for example)? What is the difference between a ...
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149 views

Lambert conformal conic isn't actually conformal?

Mathematically a conformal map has the property that the Jacobian of the transformation is a scaled version of a rotation matrix. The transformation involved in a spherical Lambert conformal conic ...
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1answer
495 views

Geometry Projection Speed Test

Lately I've been using the OGR projection classes that come with ogr/gdal, but pyproj was recommended to me, so I thought I'd give it a try. To help me decide if I should make the switch, I did a ...
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831 views

Bertin 1953 map projection settings

I am trying to use the Bertin 1953 map projection, as described in the book "Semiology of graphics" by Jacques Bertin. But I can't find the settings in any of my GIS software. Does anybody have a ...
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228 views

What are pros and cons of forcing square pixels on reprojection?

I am using Erdas Imagine 2014 to reproject 4-band raster data from GRS 1980 NAD83 Lambert Conformal Conic (ft) to UTM GRS 1980 NAD83 North UTM Zone 11 (m). Unlike ArcGIS, Erdas provides the option to ...
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130 views

Best practices and examples of web maps of polar regions

I am looking for examples of web maps focusing on polar regions (Arctic or Antarctic) preferably using a polar projection. What could be best practices to follow for such web mapping applications? Any ...
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1answer
3k views

Leaflet and EPSG 4326 Projections

UPDATE: LEAFLET fixed support for EPSG 4326 (LL84) in the latest betas: https://github.com/Leaflet/Leaflet/issues/1207 Leaflet says it supports EPSG 4326 (Plate Carree, aka ll84) projections. I think ...
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1answer
645 views

Determining Natural Origin for a GeoTIFF file (Lambert Conic)

I am trying to display an existing GeoTIFF file (from the FAA WAC set) in an application that requires the GeoTIFF NaturalOriginLongitude tag (FalconView 5.1.1). There are some older files in that set ...
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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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Converting latitude and longitude into northing and easting?

I have the following UK postcode dy8 3xt and know that the latitude and longitude is:- 54.452772 -2.156082 I also know that the Easting, Northing for the postcode is:- 389490 283880 However ...
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Southern hemisphere projections for Landsat upsets GRASS

Hi All does anyone have the last word on why Landsat scenes don't project in the southern hemisphere. This causes no end of trouble in GRASS, less so in QGIS. What I mean is, take an original scene ...
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1answer
8k views

How to re-project shapefiles?

I wanted to re-project a QGIS project, but there is no such option. When searching for an answer I see ogr2ogr suggested for this task, by re-projecting each vector layer (shapefile in this example). ...
6
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2answers
508 views

What projection does the global climate region map from Wikipedia use?

I would like to use this global climate region map from Wikipedia as a "basemap" (by plotting over the image in R). Is it possible to determine the projection of this map?
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2answers
962 views

Identify what projection this Australian map uses?

Im looking to put this map into google maps as custom tiles, but i now learn what projection is and that this map does not use the same format as google's default. You can create custom projections i ...
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1answer
141 views

What is my coordinate system preserving?

I'm trying to get a better grasp of coordinate systems, datums, projections etc. I understand that certain systems preserve different things; distance, shape, angles, area. I'm wondering how you can ...
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916 views

What's a good toolchain to reproject some PNGs in plate carre to UTM?

I have some PNGs produced from Canadian DEM data. They're 1201px by 1201px heightmaps. Each one represents one quarter of a degree latitude and one quarter of a degree longitude. But I want to work ...
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2answers
3k views

Transformation parameters for Everest datum to WGS84

I have a shapefile with the following projection information: ...
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3answers
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Using ArcMap, how may I convert a shapefile to use decimal degrees?

I have a shapefile that currently uses meters as the measure for its coordinate system, but the map framework I wish to use expects decimal degrees. I'd like to reproject my shapefile to use decimal ...
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1answer
12k views

Transforming GCS_North_American_1983 to GCS_WGS_1984 using ArcGIS Desktop?

I posted Is there projection issue with Natural Resources Canada (NRC) Canada Atlas hydrology data? describing a shift in some of the NRC data (not all). Apparently, this shift has to do with ...
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2answers
173 views

Why has an orthographic projection been used in this NatGeo map?

I'm wondering why this maps uses an orthographic projection, resulting in 3 maps to view the whole world. What were the requirements or the reasons to choose this projection (why not Mercator ) ? ...
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3answers
804 views

How can I obtain the same area values provided by the Census for TIGER boundaries using PostGIS functions?

In PostGIS, how can I compute the area of Census Boundaries and obtain the same results as are provided by the Census? For example, most Census Boundaries include attributes for Land Area and Water ...
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265 views

Create a projection to emphasize a given direction in ArcMap?

Suppose one had a dataset (centered on a given coordinate) of lines that were very close together in terms of longitude but also had important turns/bends far separated by latitude. In order to map ...
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2answers
92 views

Define projection at the record level

Hopefully this isn't too dumb a question, but is it possible to define projection at the record level, instead of a whole layer or table? I want to create a "project" database for all the work my ...
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3answers
5k views

Get Lon Lat values from a GEOGRAPHY data type in PostGIS

After storing lon lat values as a GEOGRAPHY data type, how do I retrieve the individual lat lon values? Failed attempt: SELECT id, geog, ST_X(geog), ST_Y(geog) FROM locations; Error: No function ...
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1answer
743 views

Create Mercator map with arbitrary center/orientation?

I want to see a Mercator map where I choose what latitude/longitude is in the center and what direction is "north". In some sense, a Mercator map of a rigid rotation of the globe. Does such a ...
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1answer
551 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 ...
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2answers
8k views

Basic proj4 conversion UTM grid -> longlat and back

I'm a GIS novice, and am struggling to understand how to drive proj4 to accomplish what seems like a simple thing. I've googled for a couple of days, but everything I find seems to presuppose quite ...
6
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1answer
316 views

If Geographic Coordinates are unprojected coordinates, how can GIS softwares display such unprojected data on a plane?

I have been using ArcGIS and QGIS regularly for about 2 years now, and just recently I was struck by this new thought. If a data set in say, in ArcMap, has been georeferrenced with a Geographic ...
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741 views

Calculating projected distance using ArcObjects?

I am pretty new to this and I am not sure I understand all the concepts, so I might be using words wrongly or obviously not getting some details right. We mean to do those calculations within our ...
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1answer
1k views

Problems with lat long projection

I have a .xls spreadsheet with about 60,000 rows. Most of them have Latitude and Longitude. I simply want to display these as points in Arc10. I've tried making a .dbf in arccatalog and creating a ...
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1answer
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Python script to convert Lat Long to ITM (Irish Transverse Mercator)

I am currently working on a python script that converts Lat Long (WGS84) to ITM. The formulas used are based on a paper published by OSGB (Appendix B): ...
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2answers
724 views

Using Python, Batch Project output won't drop into feature dataset?

When attempting to batch project in ArcGIS 9.3 or 10 (using either arcpy or arcgisscripting), I cannot get my geoprocessing results to drop into the feature dataset that I specify. The results ...
6
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1answer
900 views

SRID error in mapserver

I've created a network topology using QGIS, saved it as a shp, imported it into PostGIS using shp2pgsql and I'm now trying to output some of the geometry using mapserver. Unfortunately mapserver is ...
6
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2answers
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How do I use GDAL to convert from an arbitrary projection/datum into Equirectangular/WGS84?

I've been trying to use GDAL to convert from an arbitrary projection/datum into Equirectangular (aka Plate Caree, aka Equidistant Cylindrical, aka Geographic, aka Lat/Long) with WGS84 datum. All of ...
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1answer
156 views

Is there a name for map projections that produce two disks?

I've seen lots of world maps in the shape of two disks that touch, each one a separate projection of one hemisphere onto a disk -- usually the Western Hemisphere and the Eastern Hemisphere -- so ...
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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: ...
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2answers
69 views

Inferring lat/lon based on known location coordinates

I have a point dataset with a set of coordinates that is in an unknown projection. For some of these points I know the unprojected latitude and longitude. Based on these known data points, would it be ...
6
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1answer
849 views

Coordinate system in aerial imagery

I am calculating WGS84 coordinates of points in an aerial image, given the WGS84 coordinates of the center of the image and the ground distance width and height (calculated from altitude and lens ...
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1answer
242 views

Is there a difference between projecting shapefiles then rasterizing & rasterizing shapefiles then projecting?

I currently have a project where I rasterize shapefiles into simple presence/absence (1 & 0) rasters and then add each one to a running total to create a total richness raster at the end. The ...
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2answers
877 views

Is it possible to use the Goode Homolosine projection in QGIS?

Is it possible to use the Goode Homolosine projection in QGIS? Both QGIS and GRASS seem to have trouble with the interruptions, squashing the higher latitudes together. I tried +proj=goode ...
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1answer
239 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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676 views

Getting the projection of a LAS file using liblas?

I am using the python api of liblas to read/write las files. I would like to get the spatial reference information of the las file using liblas, but have been unable to figure it out. Can anyone ...