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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 ...


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 ...


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 ...


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

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

When talking about geographic locations, we usually say and use Lat-long. This has been codified in the ISO 6709 standard. When dealing with Cartesian coordinate geometry, we generally use X-Y. Many GIS systems, work with a Geographic Location as a special case of a 2 D coordinate point, where the X represents the longitude and Y represents the Latitude. ...


4

You can use ST_Transform in your first query too. select sitename, st_astext( ST_Transform( the_geom, 4326 ) ) from sites_tbl;


3

For proj4, the signs of the parameters have to be reversed. See this definition page: http://www.spatialreference.org/ref/epsg/62826405/prettywkt/ GEOGCS["Pointe Noire (deg)", DATUM["Congo 1960 Pointe Noire", SPHEROID["Clarke 1880 (IGN)",6378249.2,293.4660212936269, AUTHORITY["EPSG","7011"]], ...


3

You have entered the GCP coordinates in degrees, probably read from the imprinted degree grid. In that case, you have to set the CRS to EPSG:4283 (GDA94), which is the unprojected CRS for your EPSG:3112. EPSG:3112 has metres as units, not degrees. EDIT Another choice of doing the georeferencing is to create a vector grid in EPSG:4283. This is what ...


3

The solution--- taken from the creator of RGeo himself, Daniel Azuma, in his rubyconf talk, which is hosted on youtube here: http://www.youtube.com/watch?v=QI0e2jkUbkk, his slides are here: http://speakerdeck.com/u/dazuma/p/getting-down-to-earth-geospatial-analysis-with-rails in db migration add_column :model_names, :shape, :spatial, :srid => 2264 in ...


3

Don't set the layer CRS to WGS84 if they are in ETRS89! You are giving QGIS the misleading information that these layers contain data in WGS84 and therefore QGIS won't reproject the geometries anymore because it thinks they already are in degrees.


3

To me, your basic approach appears sound yet overly complicated. I'd start with this: scale_x = (img_right - img_left) / (x_right - x_left) scale_y = (img_top - img_bottom) / (y_top - y_bottom) new_x = img_left + scale_x * (x_in - x_left) new_y = img_bottom + scale_y * (y_in - y_bottom) You may need some minor variation due to screen Y coords being in ...


2

In ArcGIS 9.3, the Project Tool doesn't support custom geographic transformations. We also hadn't added MGI 1901 yet. There is a tool, Create Custom Geographic Transformation, that allows you to create a custom geographic transformation which is saved in a .gtf file and can then be used in the Project Tool or in ArcMap. You have to be careful to match the ...


2

If you have ArcGIS 10.1, I would change the second transformation to "Datum_73_To_WGS_1984_2009_7par". It uses the same parameters as EPSG:5037, Datum 73 to ETRS89 (5). That transformation is listed has having an accuracy of 2m, but the accuracy should still be better than the one you're using. There's also a more accurate 7 parameter transformation for ...


2

According to this (ArcMap automatically loads one geographic transformation. It's designed for the lower 48 states of the United States and converts between NAD 1927 and NAD 1983.) For datum transformations, you need to pick the transform yourself. This article goes into NAD83 <-> WGS84 choices. Projection changes can be done on the fly ...


2

Convert the file to WGS84 gdalwarp in_test.vrt out_test.vrt -t_srs "+proj=longlat +ellps=WGS84" Calcualte the bbox with GDAL in Python import gdal ds = gdal.Open('out_test.vrt') cols = ds.RasterXSize rows = ds.RasterYSize geotransform = ds.GetGeoTransform() bb1 = originX = geotransform[0] bb4 = originY = geotransform[3] pixelWidth = geotransform[1] ...


2

ST_Transform(st_geomfromtext('POINT(" . addslashes($data[6]) . ")',29903), 27700) First you create your point in irish system with st_geomfromtext(..., 29903) and then you transform it to another system, in this case 27700. ( I assume that those srids are correct)


2

There are different 2D adjustment methods because there are different sources of deformation. 1) deformations due to acquisition of an image by a remote sensor (central projection or push-broom) 2) deformations due to the representation of the Earth surface on a 2D plane 3) local errors My rule is to use the simplest method possible (the one that ...


2

Your transform goes from WGS84 to mercator. However, the coordinates of your bounds are not in WGS84 (a geographic coordinate system , with lat/long in degrees). Maybe your coordinates are already in mercator, or you should try to identify the correct coordinate system of your source before projecting the data.


2

I think you are almost there: If you post your workspace (or screenshot would be easier to follow) What I think you are missing is the BoundsExtractor for your polygon (rather than the vertices) http://docs.safe.com/fme/html/FME_Transformers/Default.htm#Transformers/boundsextractor.htm *2014 FME Desktop used here (looks different to 2013)


2

Sure, you should be able to go to Toolbox->Data Management->Projections and Transformations->Feature->Project. There, simply select your dataset and then click the button for output coordinate system, where you can browse to Projected Cordinate Systems->UTM->WGS 1984->Northern Hemisphere->WGS 1984 UTM Zone 33N.prj and press Open, Apply then OK. If you ...


2

the datum of BNG is GCS_OSGB_1936. When you project the data (or move to lat/long coordinate), you should also make sure that you set the correct datum transformation. Usually, any transform that you would choose in ArcGIS is precise enough for common mapping needs, but ArcGIS is not transforming datums by default in case of projection.


2

projections of vector datasets are not lossy in theory (if you don't have rounding errors, of course, which will depend on your software and your data storage precision). You should however be careful with projection of raster datasets, which are lossy because of the resampling. Now, if you change the datum (from one geographic coordinate system to ...


2

Some kinds of transformations are lossy. Transverse mercator for example can only be used for the visible half of the globe. The back side gets lost when you try to re-transform. Mercator only looses the poles, because it is accepted that the cylinder is unrolled in a world map. This is important if you have huge shapefiles, e.g. complete Russia or the ...


2

You can perform raster algebra using the Raster Calculator (Spatial Analyst). The syntax would be like the following: Float(Ln("flowAccumulation.img"))


2

Try this below. ST_AsText returns the well-known text. ST_X and ST_Y return the actual longitude and latitude (assuming geom is in the appropriate SRS). SELECT ST_AsText(geom), ST_X(geom), ST_Y(geom) FROM table Hope it works.


2

ogr2ogr provides 3 command line options dealing with coordinate systems -a_srs srs_def: Assign an output SRS -t_srs srs_def: Reproject/transform to this SRS on output -s_srs srs_def: Override source SRS The one you are looking for it -t_srs to transform, though you may also need -s_srs if your source data does not have it's coordinate system ...


2

The AB_CSRS file seems to have been replaced with abcsrsv4.dac. Esri hasn't added another transformation to use the new file yet (we don't have a copy). You could rename it and use the NAD_1983_To_WGS_1984_8 transformation, or create a new transformation with the geoprocessing tool, Create Custom Geographic Transformation. You will still have to change the ...


2

I'm not sure who you consulted, but this doesn't seem like great advice. The problem seems to be not one of negative values but more the order of x and y co-ordinates. A latitude (y) can only be in the range of -90 to +90. Longitude (x) can be -180 to +180, broadly speaking. These co-ordinates are from the equator and the Greenwich meridian, respectively. ...



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