Tag Info

New answers tagged

1

A Coordinate Reference System contains two different elements The datum: It defines how the CRS is related to the earth (position of the origin, the scale and the orientation of coordinate axis) e.g. ED50, ETRS89. The datum can be a geodetic datum, a vertical datum or a engineering / local datum. The coordinate system: describes how the coordinates ...


5

CoordinateReferenceSystem is the base Interface from which all other GeoTools SRS are derived from - it is the base class of Geocentric and Geographic projections (and others with vertical and temporal coordinates). It comes from the ISO19111 specification by way of the OGC GeoAPI project. CoordinateSystem is also an interface that comes from ISO19111 and ...


1

I always prefer coordinates in latlon WGS84 because they are usable worldwide and easy to understand once you know which is latitude and which is longitude. I happen to live in a country that spans across several UTM zones, and before that used several smaller Gauss-Krueger zones. As long as you are within one zone, everything is ok, but cross-zone ...


0

From a visualization point of view I was though you should use projected coordinate systems for even things on a US State size scale. Any size State that is broken into multiple State Planes, looks best in a Web Mercator or WGS projection. When you get to a region or city level, most data looks a little better in a state plane or utm projection.


3

If you load an unreferenced raster into the georeferencer, the question for the CRS is surely useless. The referencing assings values of pixel/line to target coordinates, so the source CRS does not play any role. The target CRS however is important, it depends on the way you are doing the georeferencing. You have lat/lon grid lines imprinted on the map, ...


2

"Erroneous" is relative to your accuracy needs. Let us therefore estimate the accuracy in terms of the distance the boat has traveled: by means of such a result, you can decide when positional calculations become "erroneous." I understand the question as saying that mapping is carried out in an azimuthal equidistant coordinate system centered at the boat's ...


2

Yes, the location central meridian will change the pattern of distortions in most map projections. In the polyconic projection the length of the central meridian is correct, and also along latitude lines (which are not straight). The latitude of origin doesn't affect the pattern of distortions, but only sets the Y (Northing) = 0 location. For China, if your ...


4

Thanks to Chris W., we were able to find a solution to the problem. In ArcGIS Pro, the coordinate system in ArcGIS Pro for scenes does not initially conform to the layer coordinate system as it does in ArcGIS for Desktop. In ArcGIS Pro you have to specify a coordinate system manually. When a new map or scene is created, the default coordinate system is WGS ...


1

You can use Field Calculator to get highly accurate geodesic lengths of features in a feature class, regardless of the coordinate system. This means that Arc will find the shortest route across the surface of the ellipsoid when connecting vertices of your lines. Here's how to do it: Open the attribute table of your line feature class. Add a new ...


1

No, In fact arc map uses map units or page units for label offsets so this distance is not related to projection anyway. As ESRI says "These units are measured in map units or in page units (millimeters, inches, or points)." So there is no matter if the layer is in GCS or PCS. Details are at here and here.


1

The best way to find out which layer is correct, is to set the project CRS to EPSG:3857 with on-the-fly-reprojection enabled, then load a Google or Openstreetmap background via the OpenLayers plugin, then add your layers and check their layer CRS. Then you see which layer ist placed on the right spot, and which might have a wrong CRS. BTW this page ...


0

You can use PostGIS for this. To perform vertical datum transformations, you'll have to add your own SRID to the spatial_ref_sys table with the appropriate WKT and proj4 parameters. For example, if you query the spatial_ref_sys table for NAD83(CSRS) UTM12 (EPSG:2956), select proj4text from spatial_ref_sys where srid=2956; you get: +proj=utm +zone=12 ...


0

Converting the units to degrees, you can use this header file: nrows 21600 ncols 43200 nbands 1 nbits 8 layout bsq skipbytes 0 ulxmap -179.996 ulymap 89.996 xdim 1 ydim 1 to perform a simple gdal translation with: gdal_translate -a_srs "+proj=latlong +r=6370997" -a_ullr -179.996 89.996 179.996 -89.996 goge2.bsq destfile.tif to get ...


1

Thank you @mkennedy for your input. I am posting an answer to my own question in case anybody stumbles across this issue. From this website here, I was able to download the same dataset, but as .tif with pre-defined CRS. Go to the EarthExplorer from this aforementioned website, choose "Land Cover / GLCC" and take the .tif file. Registration (free) is ...


0

No, it will not work (unless you're just using the import to define the CRS to what you know it is supposed to be). When importing to a feature dataset, everything must end up in the same CRS. The import process can automatically project from the source CRS to the feature dataset's, but in order to do that it has to know the source CRS in the first place. If ...


0

Because you're using vanilla ACAD, you don't have access to coordinate reference systems or the ability to save as a shapefile - that requires Map or Civil (so far as I know). This means you have plain CAD data, which uses a local, Cartesian coordinate system (ie there's an origin at 0,0 and then x/y coordinates on a flat plane). This means you'll have to ...


4

There are two things that must be done. Using your data I set the spatial reference of the shape file to WGS_1984_UTM_Zone_43N (it was undefined) and then repaired the geometry with Repair Geometry. After that the image extracted properly with Extract by Mask: This could be scripted if you have python ability but can also be done on batch.


0

I think I got this figured out. I used the Create Fishnet tool on a feature class of NAD83 State Plane CA 5 to create vertical and horizontal lines. Then I calculated the northing and easting values, in different fields, in NAD 83. After that I changed the dataframe to NAD27 and calculated the northing and easting in that system. After running a few field ...


0

There are algorithms that will transform from a grid system to another grid system without going without requiring a conversion to lat-long. So the best answer I can come up with is not always, but often they use lat-long.


3

Almost all software for doing coordinate projection use geographic coordinates as a standard system in the middle and defines "forward" (from geographic to projected) and "inverse" (from projected to geographic) routines for projections. So, to go from a UTM projection (say "UTM 10 N") to a stateplane projection (say "Washington Stateplane North") you'd ...


1

Use the function nowrapSpatialPolygons at the anti-meridian of your central longitude. This doesn't work with wrld_simpl from maptools, but it does work with countriesLow from rworldmap. library(rworldmap) data(countriesLow) library(maptools) prj <- "+proj=robin +lon_0=-198 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs" x0 <- ...


0

Myanmar Datum 2000 Everest 1830 a = 6377276.345 f = 0.00332445 1/f = 300.8017 Xshift -246.632 Yshift -784.833 Zshift -276.923


0

I used the Vector --> Analysis Tools --> Distance matrix to find out the distance between the points in Point Layer and then in the resultant file generated .csv multiplied distance column with 111.32 to get the distance in Kms. I verified the results by comparing it with actual distances Hope this help


2

A very simple brute force approach: take the first points coordinates and convert them from ISN93 / Lambert 1993 to WGS84 degrees using cs2cs in the OSGEO4W shell cs2cs +init=epsg:3057 +to +init=epsg:4326 -f "%%.8f" <ISN93.txt >WGS84.txt build a local omerc CRS on that point, with the "local coordinates" as false Easting and Northing convert the ...


0

For what you are trying to do you could use the WMS datastore in GeoTools to import the layers you need: see https://gitlab.com/snippets/6355 for a full example.


0

If you don't define SRID for the geometry column at the time of its creation, you can insert geometries with any SRID. I can't think of a reason you would want to do that though. It's reasonable to store all geometries with the same SRID. I see three options you have: create new geometry column and fill it with st_transform(geom1, new_srid) use ...


3

I am no expert in this but from my understanding: The OpenLayers plugin in QGIS uses the EPSG:3857 CRS which is a projected CRS on a flat surface (here's a very good post describing it). Therefore, it calculates a straight-line distance as you would on a paper map. I can't find how Google Maps calculates its distances but a common method would be to use ...


1

First part is getting the point cloud on the correct scale, this can be done with GCP that are set to known real-world co-ordinates, or tied to GPS. Measurement functionality isn't present within VisualSFM, so Meshlab will need to do the job for you. Once you have imported the PLY file that visualsfm has generated into Meshlab, click edit, Measuring tool. ...


1

Have you checked out the tool Regular Points? I believe this is what you are looking for. It can be found under Vector - Research Tools - Regular Points...


2

KML files use WGS84 LL by default, so yours should appear correctly positioned with respect to another dataset that you are confident is georeferenced (such a reference dataset is very useful when importing new data) However if the DXF file has not been supplied with any description of the coordinate system used then you have a few options. Ideally you ...


1

Error 000289 is probably an ArcGIS error message. The complete description says: The spatial reference of the dataset cannot be altered. The dataset may be in use by another application and therefore locked. The error message makes it sound like you tried to use Define Projection or the data's property page to change the coordinate system. That ...


0

If your image uses paletted colours, you have to translate it first to RGB colours: gdal_translate -expand rgb src_dataset dst_dataset If your image is not placed correctly when loading into QGIS, use gdal_translate -a_ullr to set the bounds. Since Openstreetmap uses EPSG:3857, you can directly reproject your image to that projection with gdalwarp ...


2

You can create a custom CRS with these parameters: +proj=omerc +lat_0= -22.5 +lonc=25.09 +alpha=0.910238 +k=0.99977264 +x_0=0 +y_0=0 +gamma=0 +a=6378249.145 +b=6356514.966398753 +towgs84=-143,-90,-294,0,0,0,0 +no_defs +to_meter=10000 And you get the 10km-grid as described: I took the old ARC 1950 datum from EPSG:4209 as base, which was common in ...



Top 50 recent answers are included