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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.


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As the Douglas Peucker algorithm works by iteratively removing those points that are within a given tolerance from some line between two other points in some given input unit, you can assume that if you have a geometry covering a large north-south distance, you will get greater amounts of simplification for a given tolerance in degrees as you move further ...


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The EPSG: 3857, WGS 84 / Pseudo Mercator in QGIS is called WGS84 Web Mercator (Auxiliary Sphere) in ArcGIS. You are simply not using the right projection.


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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 ...


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You should also change the CRS of the project by clicking the grey planet on the bottom right:


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If you view the layer in QGIS with On-the-fly-reprojectionenabled (which is default if the loaded layers have different CRS). you will not see any difference. That is the deeper sense of reprojecting: The object stays on the same spot on Earth, but the coordinates change. If you turn off otf, you will see the layers on different places after zooming to the ...


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 ...


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ArcGIS supports spheres or ellipsoids (spheroids) with the azimuthal equidistant projection. Here's a sample prj (wkt) string for "World_Azimuthal_Equidistant" based on WGS 1984. PROJCS["World_Azimuthal_Equidistant", GEOGCS["GCS_WGS_1984", DATUM["D_WGS_1984", SPHEROID["WGS_1984",6378137.0,298.257223563]], PRIMEM["Greenwich",0.0], ...


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I set the data frame projection to WGS84 Web Mercator (Auxiliary Sphere) as suggested by Nahas and this didn't change the end result. However looking at the previous thread supplied by Vince (QPJ files on ESRI software) the answer at the bottom suggested deleting the prj. and .qpjs files then bringing the data in. I did this, assigned projection to WGS84 ...


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Rightclick -> Saxe As ... to reproject a layer only works for vector layers. Raster layers are a bit more complicated, you have to use Raster -> Projections -> Warp(Reproject) with a new file name and source CRS different from target CRS.


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You have to specify the projection on a sphere, because proj seems to only support the spherical formulas of this projection: +proj=aeqd +R=6371000 +lat_0=51.0246 +lon_0=-113.3981 For some example plots, see Manipulating Azimuthal Equidistant Projections in QGIS


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The documentation for Near Analysis indicates "NEAR_DISTANCE: The distance between the input and near feature. The value is in the linear unit of the input features coordinate system, or Meters when the Method parameter is set to GEODESIC and the input is in a geographic coordinate system." So my understanding of that statement is: A Geographic Coordinate ...


1

"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 ...


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So after discussing this problem with other developers in Gdal-Dev mailing list it turned out that MODIS swath data can not be perfectly re-projected by using gdalwarp. It is because of bow-tie effect of the MODIS scanning sensor which gdal can not deal with. The best option is to download associated geolocation datasets (MOD03) and use MRTswath for ...


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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 ...


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If I understand correctly, your LAS is already classified, so you could project it first, then convert to multi-points. The Projections and Transformations toolbox offers a Raster toolset which includes the ProjectRaster tool. Or, if the problem is actually with the conversion to multi-point, make sure your input class options are defined. I'm not a LAS ...


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It is due to the projection of a 2D plane onto a polorised 2 spheres surface, as the line moves past the poles, it becomes distorted as far as observers of the 2D plane are concerned because the straight line to the destination appears to be a curved ark of a Great Circle, which is a term in mathematics that relates to the greatest circle that can be sliced ...


1

Double Stereographic vs Stereographic. Mathematically a stereographic projection is directly projecting the sphere to the plane. A double projection is projecting to another mathematical spheroid first (Guassian Spheroid). Both projection centers are located on opposite the tangent point of the plane (ie on the other side of the planet). Why use either ...



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