Tag Info

Hot answers tagged

15

Yep sure can. Like alexgleith said you can use the qgsaffine plugin (from the plugin installer) The top of the first line is at 0,0 and the top of the second line is at 5,5. At the start the points are along 0 on the X. Using the Affine plugin we can add 5 to all the X coordinates: Then after they are all on the second line at X 5, Y 5:


12

One simpler way would be to use the GDAL command line tools: gdalwarp infile.tif outfile.tif -t_srs "+proj=longlat +ellps=WGS84" That can be invoked easily enough via scripting for batch jobs. This will warp the raster to a new grid, and there are other options to control the details. http://www.gdal.org/gdalwarp.html The target (t_srs) coordinate ...


12

Note/Disclaimer: I work for Esri. Prior to ArcGIS for Desktop 10.1 service pack 1 (10.1.1), we loaded one geographic/datum transformation in ArcMap: NAD_1927_To_NAD_1983_NADCON (using the conus grid files). For 10.1.1, that was removed. All other transformations must be user-selected using the Transformations dialog. You can launch this dialog from the data ...


11

As mdsumner said, it's much easier to use command line than the python bindings, unless you want to execute very complex tasks. So, if you like python, like I do, you can run the command line tool with: import os os.sys('gdalwarp infile.tif outfile.tif -t_srs "+proj=longlat +ellps=WGS84"') or iterate through a list o files: listoffiles=['file1, file2, ...


10

Actually, you will want gdalwarp, not gdaltransform. There are lots of examples out there. For example, gdalwarp -t_srs 'EPSG:4326' input.tif output.tif


10

In order to get the coordinates in decimal degrees, the data needs to be reprojected to WGS84. import ogr, osr driver = ogr.GetDriverByName('ESRI Shapefile') shp = driver.Open('testpoint.shp', 0) lyr = shp.GetLayer() feat = lyr.GetNextFeature() geom = feat.GetGeometryRef() # Transform from Web Mercator to WGS84 sourceSR = lyr.GetSpatialRef() targetSR = ...


9

Responding to the question in the subject line and ignoring the body, please see About geographic transformations and how to choose the right one. The quick list: NAD_1983_To_WGS_1984_1 - for the entire North American continent. NAD_1983_To_WGS_1984_2 - for the Aleutian islands. NAD_1983_To_WGS_1984_3 - for Hawai'i. NAD_1983_To_WGS_1984_4 - superseded by ...


9

A transformation should be used to "transform" between two systems such as geographic coordinate system (GCS) and Projected Coordinate System (PCS). There are other instances for it's use also. Link #3 is the ESRI 9.3 help page that is pretty good about describing the difference. Way too much detail for me A little more Lay description Just right To ...


9

You can see the proj string used by QGIS to transform from and to WGS84 when you look at Settings->Project settings, CRS tab, and search for the EPSG code or name of a CRS. All CRS are referenced by their EPSG code, or user defined CRS. Uusally, all EPSG-codes are bundled with one certain transformation to WGS84 which was decided to be most ...


8

Gdalwarp is the tool to reproject, you find it in Qgis under Raster->Projektionen->Transformieren or standalone in OSGEO4W. Basic command is gdalwarp -s_srs EPSG:25832 -t_srs "+proj=tmerc +lat_0=0 +lon_0=6 +x_0=2500000 +y_0=0 +k=1.000000 +ellps=bessel +units=m +nadgrids=./BETA2007.gsb +wktext" input.tif output.tif BETA2007.gsb should be in the same ...


8

I'm assuming that your input lat-long are based on the WGS84 datum. Making a point geometry under this assumption is as easy as using the ST_MakePoint() function: The problem with ST_MakePoint() is that the geometry that is created does not not have a spatial reference. We can set the spatial reference by using the ST_SetSRID() function. So the simplest ...


8

First, Proj4 uses what EPSG calls the "Position Vector" version of the 7 parameter method. It's possible that GeoTrans and Leica GeoOffice use the other version which EPSG called "Coordinate Frame". Both methods are equivalent, but the rotation matrices are different and the signs of the angular parameters have to be changed. Second, thank you for ...


7

You can try the DotSpatial.Projections library. The website lists an example "Converting from a Geographic Coordinate System to a Projected Coordinate System": using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using ...


7

The transformation failed for your case since the UpdateGeometrySRID command just changes the metadata, but does not transform coordinates. And when you attempt a transform from 4326->4326, no transform is done since the SRIDs are equal. If you have PostGIS 2.x with a table like this: CREATE TABLE my_table ( gid serial primary key, geom ...


6

In GRASS you can use v.transform for this on vector data: Performs an affine transformation (shift, scale and rotate, or GPCs) on vector map.


6

I see you are from Sarajevo so you are probably need to convert GK coordinates from B&H coordinate system. First you will need to get transformation parameters for your area. I don't think there are any good one in EPSG database. Maybe you can use this one. I sometimes use them for area of Croatia. Regarding the C# lib, there is one which I used ...


6

Looks like Thompson Falls, MT. The current state plane coordinate system (1983) for Montana projects (-115.326662 47.582952) to (162339, 386636), which is (133, -55) meters off: not awful, but not good, either. You could be using a custom datum or maybe your site coordinates are actually off by that much. It's unlikely any other standard coordinate system ...


6

OpenLayers can transform vector layers (like WFS). If your vector layer is in EPSG:900913 or EPSG:4326 OpenLayers can handle the transformation itself, otherwise, it needs Proj4js included. There are examples of how to use OpenLayers with Proj4js. Raster Layers cannot be transformed by OpenLayers. If you need to include them in a different projection, you ...


6

As long as the Char fields all contain floating point numbers, then I doubt you would need to do this at all. FME doesn't generally care about data type within the transformation, and will only care about it on writing if the data doesn't match the required type. i.e. as long as your char strings are all valid as floats, FME will do the conversion when the ...


6

The formula and its application are basically correct: the length of the Equator is 2 * pi * R and equating that with 707 pixels tells us the scale of the map at the Equator. However, any formula involving trigonometric functions of angles that involves pi expects the angles to be given in radians. Therefore, the Mercator position of latitude 51 degrees ...


6

You can compare the two. In most applications I suspect the second (direct) method will be the one to choose. Accuracy of the first (iterative) method depends on the accuracy with which you do the computations and when you decide to stop iterating. It therefore can be made as accurate as the second method for all inputs where both are valid (the first ...


6

As om_henners advised it is better to use available library for this purpose as it is already implemented and tested by many people... So, take a look at pyproj Python lib. Here is a sample code for reprojecting WGS-84 long/lat to ITM (EPSG:2157) x,y: from pyproj import Proj, transform def reproject_wgs_to_itm(longitude, latitude): prj_wgs = ...


6

Sightings constitute a (non-random) sample of some process or population. Accordingly, interpolation (especially) IDW is not a good idea: it solves a different problem altogether. Consider making a density map. When doing so, it's probably better to favor equal-area projections over conformal projections (because changes of area bias the density, whereas ...


6

If you just want to convert coordinates from one CRS to another, the GDAL Tool cs2cs does what you want in an easy way. QGIS uses the same library in the background, so you will get the same results. GDAL uses the PROJ4 library to convert CRS and datums, so this is where to look up what is actually calculated. For converting NAD27 to NAD83 and WGS84, PROJ ...


6

Modern mathematics characterizes transformations in terms of the geometric properties that are preserved when the transformations are applied to features. A time-honored example is the set of Euclidean transformations of the plane: these are the ones that preserve all distances and (unoriented) angles. The study of this group of transformations is the ...


5

If you can perform the transformation client-side, you can take advantage of Proj4JS (user guide) which is a Javascript port of the underlying Proj.4 library. If you're doing this Server-side there's a C# wrapper for Proj.4 which could also be used. If this is a conversion that doesn't need to be done dynamically, then using GDAL as glennon mentioned is ...


5

Look into GDAL. For a shapefile, the conversion command will be something like: ogr2ogr -f "ESRI Shapefile" output.shp -t_srs EPSG:4326 -s_srs EPSG:31468 input.shp Bindings for GDAL in C#: http://trac.osgeo.org/gdal/wiki/GdalOgrInCsharp


5

To add to Andy W's comment/answer: You could (should) generate a test dataset with cross-checking via multiple different 3rd-party re-projection APIs, giving you more confidence that you're not just reproducing, for example, a proj.4 bug. Also, you can create various identities, modulo floating point error, that you can test in a randomized way -- e.g. ...


5

If this question concerns interpolating the projected coordinates from a printed map or display, the answer is easy: you can always linearly interpolate. This is because the world-to-display transformation is affine (and doesn't involve a projection at all). So I presume you are concerned about interpolating spherical coordinates; that is, lat/lon. No ...


5

Use the Petroleum Transformation in your project parameters for more accurate results: OSGB36_To_WGS84_Petroleum - this seems to be a 7 parameter Helmert transformation and seems to use the parameters suggested by the UK Ordnance Survey. As such, it's accuracy should be 5m at worse. http://forums.esri.com/Thread.asp?c=93&f=984&t=132296 Have had no ...



Only top voted, non community-wiki answers of a minimum length are eligible