The process of translating a map or spatial data from one geographic projection to another

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53
votes
8answers
2k views

One dimensional map of the world?

Bit of a strange question but hope this is OK to ask here. Has anyone heard of a '1-dimensional' projection of the world map - that is mapping all the points on the globe to a single line? I was ...
36
votes
3answers
41k views

Layers with same coordinate system should align/overlap but do not?

I put 4 different layers into my ArcMap document, but only one of them will show up on the map! I should be seeing the other 3 layers as well. When I do a Zoom to layer, I can see one layer, but I ...
28
votes
1answer
3k views

Coordinate system for calculating areas of polygons accurately?

I have multiple polygons, all located offshore around the UK. I am trying to calculate the areas of these polygons in square kilometres, without splitting them by UTM zone. Is it possible to do this ...
25
votes
3answers
10k views

How to reproject all geometries in a PostGIS table?

I created a spatial table with SRID:4326. Now I want to change total projection to SRID:32644 into a new table. The old table should remain unchanged.
25
votes
2answers
17k views

What is the difference between EPSG:900913 and EPSG:3857?

I'm using the QGIS google layers plugin to digitize a parcel as a shapefile. Later I want to import it to PostGIS. I know that google maps use a special 'google mercator' projection. What is the ...
21
votes
2answers
21k views

How to reproject a vector layer in QGIS?

I have some shape file which is in UTM. I wanted them to convert to Decimal Degrees in QGIS.
19
votes
5answers
13k views

Map projection in OpenLayers

I want to overlay some data whose projection is WGS-84 on Google map layer in OpenLayers. But I just can't make them in the right place. I did as follows: map = new OpenLayers.Map('map', { ...
15
votes
1answer
15k views

Projecting sp objects in R

I have a number of shapefiles in different CRSs (mostly WGS84 lat/lon) that I'd like to transform into a common projection (likely Albers Equal Area Conic, but I may ask for help on choosing in ...
14
votes
5answers
2k views

Does Re-Projecting ShapeFile only update content of *.prj file?

if i wish to change the projection of some shapefiles from .. lets say NAD83 (4269) to WGS84 (4326) ... and by using some 3rd party app .... does this mean the .prj file is only updated .. and not the ...
12
votes
3answers
500 views

Does transforming to a new projection, then back, affect data accuracy?

I have a feature class (South Carolina counties, so a fairly large geographic area) in NAD83 SC State Plane. It needs to be transformed to a second projection (NAD83 UTM 17), then transformed back to ...
12
votes
2answers
10k views

Is there any online tool for converting coordinates between different EPSG?

Every time I want to do conversion, I need to get into the console to run proj.4. Is there any online tools for converting coordinates between different EPSG?
12
votes
2answers
2k views

Reprojecting WGS 1984 Web Mercator (EPSG:3857) in Python with GDAL

I am reprojecting rasters in python using GDAL. I need to project several tiffs from geographic WGS 84 coordinates to WGS 1984 Web Mercator (Auxiliary Sphere), in order to use them later in Openlayers ...
11
votes
10answers
11k views

Batch convert lat longs to UTM?

I've got a .csv file that contains a long list of latitude and longitude points. Is there an efficient way to batch convert the list into a projected UTM coordinate system? Thanks.
11
votes
2answers
16k views

How to enable projection transformation in QGIS

My QGIS project has two layers, one layer is retrieved by Google layer plugin which fetches the static Google map image whose CRS is +proj=merc +lon_0=0 +lat_ts=0 +x_0=0 +y_0=0 +a=6378137 +b=6378137 +...
11
votes
2answers
2k views

How can I improve my Georeferencing results?

Background This is my second question related to georeferencing naked raster maps in order to re-visualize them on different coordinate systems and in conjunction with other data layers. The previous ...
10
votes
3answers
12k views

Converting X,Y coordinates to lat/long using pyproj and Proj.4 returns the wrong coordinates

I'm writing a python script that reads multiple XML files containing x and y coordinates and combines them all into a single csv file. Latitude and Longitude are required fields in the csv, but I am ...
10
votes
2answers
4k views

Derive WGS84 Longitude & Latitude from British Northings & Eastings

I'm looking for a fairly simple way to append columns with WGS84 longitude and latitude to a table containing northings and eastings. The source data is Ordnance Survey's CodePoint Open, which I is ...
10
votes
1answer
2k views

How can I see the coordinate transformation parameters in QGIS?

How can I see (and edit if possible) the transformation method and parameters used by QGIS for "on-the-fly" transformation, and then for saving data in another CRS? Like in ArcGIS? Here is the ...
10
votes
2answers
253 views

Why do I get correct area and intersect area when use wrong projection?

I need to calculate areas and intersection areas for polygons (some real geographical objects like lake, city, country, e.t.c.). Polygons located in California, New Zealand, Russia.Anadyr, Sweden All ...
9
votes
6answers
9k views

ArcGIS/ArcPy Python, how to get latitude and longitude of a projected point?

I have a point feature in a feature class that is being accessed by ArcPy. The point is projected but I need to find an efficient means to get the unprojected latitude and longitude for this point. ...
9
votes
2answers
1k views

why do people use geometry to represent geography?

Historically I've mainly worked with simple latitude and longitude coordinates in a SQL Server. I stored them as a geography datatype in SQL Server, and rendered them on a variety of displays (...
9
votes
1answer
6k views

How to reproject a raster file in QGIS with datum transformation?

I want to reproject a tiff raster file from projection A (ETRS89/UTM Zone 32) to projection B (DHDN/Gauss-Kruger zone 2). The two projections have a different datum so I have to use a datum ...
9
votes
1answer
389 views

Reprojection - Learning the ins and outs

I would like to expand my knowledge coordinate systems, projections and reprojecting data, with a view of writing a reprojection engine. Could you provide me with some resources (books, websites, ...
8
votes
2answers
567 views

More accurate way to calculate area of rasters

In my daily work, I am constantly asked to calculate areas of global raster datasets in geographic projection at 30 arc second resolution. These datasets are normally the result of a Combine operation ...
8
votes
2answers
602 views

How to get a “classical” globe projection

I have a shapefile of the world continents in EPSG 4326. To what reference system do I have to reproject my file to get a projecting like this globe below?
8
votes
3answers
1k views

1km circles around lat-long-points in many places in world

I have hundreds of lat-long-points spread around the world, and must create circle-polygons around each of them, with radius exactly 1000 meters. I understand the points must first be projected from ...
8
votes
1answer
232 views

Reprojecting elevation dataset for “tilted Earth”

I would like to create maps of a "tilted Earth", such as the following example where Australia is at the North Pole: http://i1048.photobucket.com/albums/s379/laskaris_mods/tilted_earth.jpg I can ...
8
votes
1answer
311 views

Looking for US National Grid to Lon/Lat Converter in Python, C, or C++

I see here that there is Fortran source code for going from USNG to lon/lat: http://www.ngs.noaa.gov/PC_PROD/USNG/ Is there some python or C/C++ code that does the same? My understanding that this ...
7
votes
2answers
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
votes
1answer
111 views

Why is there an upper limit to the SRID value in the spatial_ref_sys table in PostGIS 2.1?

I was trying to insert a reference system in PostGIS from http://spatialreference.org/, and got a constraint violation for spatial_ref_sys_srid_check. I checked that constraint and found that, when ...
6
votes
3answers
3k views

How can I find out how to convert this point to lat lon?

I have received a shapefile with measurement points to be analyzed, but no matter how I try, I can't find how to convert to lat lon. I suppose it would be good to know the projection but when I look ...
6
votes
2answers
2k views

Why do my Shapefiles not align correctly?

First: I'll summarize what I understand so far so please confirm or correct me. When On-the-Fly is selected a layer is re-projected from that of the layer's CRS to that of the project CRS, IF ...
6
votes
3answers
4k views

Using ArcObjects to choose GeoTransformation?

I’m currently building a Desktop add-in tool with ArcObjects that: Asks a user to select a feature class Reprojects the feature class to Web Mercator Executes some geoprocessing The initial ...
6
votes
1answer
141 views

Can I project a single set of coordinates that are not in a table or feature class with arcpy?

I have been searching for the easiest way to convert a single set of State Plane Coordinates (in units of "Feet") to Decimal Degrees using arcpy. All the methods I have seen so far involve one of the ...
6
votes
5answers
3k views

Can I copy an entire geodatabase with relationship classes and domains and reproject all feature classes from wgs84 to state plane?

I have an SDE geodatabase with several feature classes, tables, relationship classes, and domains. All the feature classes are currently in WGS84 coordinate system. I need an exact copy of the ...
6
votes
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
votes
1answer
2k views

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): http://www.leica-geosystems.co.uk/downloads123/...
6
votes
2answers
77 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
votes
1answer
875 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 ...
6
votes
1answer
111 views

Why does the difference between two overlapping rasters exist?

I have two similar rasters of the Mount Vesuvius: one spans 20 kilometers, and the other one 50 kilometers. Both rasters are in WGS84 geographic coordinate system, and they overlap between each other: ...
6
votes
3answers
3k views

Is it possible to change spatial reference (and reproject) feature classes in-place, using ArcMap/GeoProcessing?

We have an Esri based system in production; a complicated data model with a large number of feature classes. We need to migrate the data to another spatial reference. The feature classes have class ...
6
votes
1answer
603 views

What resampling technique should be used to reproject an altitude raster?

Does anyone know whether I should choose: nearest, bilinear, cubic or majority when projecting the WorldClim altitude raster layer?
6
votes
1answer
132 views

Should I Reproject Data Which Has Been Captured Incorrectly?

I'm working on a project for a client which is migrating data from an Oracle database to an ESRI Geodatabase. When data for this project was initially captured over 15 years ago, the coordinate ...
6
votes
1answer
2k views

Reproject script in Python with GDAL

I'm having a lot of trouble with GDAL. Besides just the at times lacking documentation, there seems to be little support in Python. Anyways this is just a batch reproject script that goes thusly: ...
6
votes
1answer
498 views

Problem reprojecting LIDAR data with Liblas [duplicate]

I am currently trying to reproject a LIDAR file (.las) using the Open-Source LibLAS, compiled on a Scientific Linux server. The Original data is in Oregon Lambert, NAD83 (EPSG:2992), and I am trying ...
6
votes
0answers
2k views

How do I solve Gdalwarp error 'too many points failed to transform' for remapping Geostationary to Lambert conformal?

I am trying to remap from Geostationary to Lambert conformal using gdalwarp. My input data is in netcdf, and is in geographic coordinates (degrees) and I would like to output the remapped data to ...
5
votes
4answers
731 views

Given long, lat, x and y, how do I find the projection?

I am using an app called farsite that outputs shapefiles that show how forest fires will grow. I am getting output in coordinates as X and Y values rather than (lon,lat) and am looking for a ...
5
votes
2answers
220 views

Lat/Long -> UK Easting/Northing?

I have a fairly accurate formula (implemented in C#), which allows me to convert UK Eastings/Northings to WGS84 Latitudes and Longitudes. Despite extensive Google searches, I could not find a formula ...
5
votes
1answer
567 views

File size inflation normal with gdalwarp?

After using gdalwarp to project and align-to-grid (via -tap) a number of rasters I noticed that the output rasters were significantly larger than the original rasters. A fairly thorough web search ...
5
votes
1answer
323 views

PROJ.4 cs2cs is too slow. Alternative?

I use PROJ.4 cs2cs to convert data from a Lambert Conformal Conic to a geodetic coordinate (NAD83) or vice versa. In my application, sometimes I need to convert a lot of data. Because I call cs2cs ...