New answers tagged

0

The scale factor – a measure of linear distortion – of national projected coordinates typically (e.g., for UTM) range between 0.9996 and 1.0010. In places this would amount to more than 1m, over large distances. However, these distortions can be calculated and hence applied. See influence-of-the-scale-factor-on-the-projection, ...


0

Is it too big a technical problem to have an orthographic projection pre-loaded, that can be re-centred to any view?


0

The projection looks like it matches this custom entry in http://spatialreference.org: PROJCS["Stereographic_North_Pole", GEOGCS["GCS_Coordinate System imported from GRIB file", DATUM["D_unknown", SPHEROID["Sphere",6371229,0]], PRIMEM["Greenwich",0], UNIT["Degree",0.017453292519943295]], ...


1

you can use an equal area projection to get the area corresponding to the surface of the Earth. Using shapely is not a problem if you use the appropriate projection. Just make sure that you densify your shapefile vertics before you project it. Examples of equal area projections include cylindrical equal area and sinusoidal projection.


21

This is an intrinsic feature of ArcGIS. Just open "Geographic Coordinate Systems" folder, then the "Solar System" folder, then choose "Mars" and the datum associated with your data.


2

I had the same problem and simply convert .xlsx to .csv only helped to display the x coordinate. I used the table to table file to create a new table from the .csv file and define the field type to be numeric. After that it worked. To me it seems to be more of an excel problem rather than an ArcGIS 10.3 problem...


0

For US-level analysis I usually use the USGS Albers Equal Area projection "USA_Contiguous_Albers_Equal_Area_Conic_USGS_version". proj4string: +proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m +no_defs EPSG: SR-ORG:7480


0

Just as a quick double check, when you rotated the coordinates, you did "rotate from the center", correct? In other words, your resulting coordinates were: {x Cos[angle] + (2 cy - y) Sin[angle], y Cos[angle] + x Sin[angle]} where cy is the center y coordinate (ie, half the y width, or 3080 in your case), and angle is the angle of rotation, correct? When I ...


5

The column format for PostGIS is called geometry and you'll probably need to read up on all the functions associated with managing spatial columns. If you are getting the lat/longs from GPS or Google, the projection will be EPSG:4326. edit: iant's comment brings up a good point about the geography type, and indeed if you are using EPSG:4326 it looks like ...


0

You thought to reproject to UTM by using Set Layer CRS, which is wrong. You have altered the CRS, but not the extent. You need Raster -> Projections -> Warp to reproject raster data correctly to another filename and CRS.


2

Example for reprojection from EPSG:2193 to EPSG:3857 c:\OSGeo4W64\bin\ogr2ogr.exe ^ -f "MSSQLSpatial"^ "MSSQL:server=DestServerName;database=DestDbName;trusted_connection=yes"^ "MSSQL:server=SourceServerName;database=SourceDbName;trusted_connection=yes"^ -sql "SELECT [Id], [Shape].STAsText() Shape FROM [SourceDbName].[dbo].[SourceTableName]"^ -nln ...


1

You do not need a projection if your coordinates are arbitrary. If you are going to use a basemap to pick a corner of the building provided by Arcmap then you are stuck with WGS84. Autocad offers free trial and complete student edition if you are a student. There are many open source drafting programs to choose from but your question does not state an OS ...


0

If you haven't draw it yet...maybe create a map from this site https://www.scribblemaps.com/ . This is free but if you want more than just free then there's a payment... What you can do is just draw a polygon and then save the map. Then after that you can send it to kml to bring it up Google Earth Pro .. Then send kml to ArcMap.


1

The process that you need to do in order to reproject your image is called georeferencing. For basic/linear georeferencing, the minimum number of points you need is 3 so if you have 4 corners you should be fine. There's a few tutorials available on the net based on Arc and QGIS tools that can show you how to perform this on raster images. I've never used ...


2

Is the raster format an Esri GRID? If so, the original LCC definition may have used NAD83 (CSRS) which isn't supported in the PRJ.ADF file format used by Esri grids. The definition doesn't match any of the existing Canadian LCC definitions, but it's close. Do try to change the geographic coordinate reference system only to NAD 1983 (North American 1983) ...


3

It looks to me like the Lambert projection file has an error. GRS_1980 is a spheroid, not a datum. The NAD83 datum is based on the GRS_1980 spheroid. I think it is possible that your Lambert projection is actually using the NAD83 datum. Your datum transformation throws an error because you are not trying to transform between WGS_1984 and NAD83. If it were ...


5

If the substation coordinates are given in latitude and longitude, the CRS can not be EPSG:32629. EPSG:4326 seems more reasonable, or a local datum with degrees as units. You should not use Set Layer CRS to cahnge the CRS, but save As ... to a different name and CRS. You can install openstreetmap background with the OpenLayers plugin to see if the stations ...


1

Answer: When adding XY data in NAD27 Decimal Degree Coordinates (from a .csv file The buffer distances will be inaccurate to the basemap if the basemap is in a different GCS (Geographic Coordinate System) or PCS (Projected Coordinate System) Solution: display XY data from .csv file export data by right-click on "filename.csv Events" select data then ...


2

The purpose of the map here will really decide which CRS you will use. You basically have 2 options, a geographic coordinate system or a projected coordinate system and depending on what you want to accomplish will help you choose which system you want to make a map in. ...


3

The best thing would be if you can speak with the person who created the layers and try to discern if they might have accidentally put something/defined something in the incorrect projection. Or maybe it was poorly digitized. I have had some success guessing if the projection is just a zone or two off and simply redefining the projection. If someone ...


3

"In Oracle, calculating the distance on WGS-84 gets me the result in degrees." That can only happen if your geometries are defined without any explicit SRID (= SDO_SRID is set to NULL). In that case, the database has no clue about what you are actually storing: it does not know that your data is actually geodetic. All it sees is some numbers that it assumes ...


2

There is a straightforward, disciplined way to analyze such data: linear regression. It can work because (a) the range of these points is a relatively small part of the world and (b) to a close approximation over such ranges, projection formulas are nearly linear as a function of latitude and longitude and--with more data--even their departures from ...


1

Have you tried specifying the units. Based on this https://docs.oracle.com/cd/B19306_01/appdev.102/b14255/sdo_objgeom.htm#i857957 "Unit of measurement: a quoted string with unit= and an SDO_UNIT value from the MDSYS.SDO_DIST_UNITS table (for example, 'unit=KM'). See Section 2.8 for more information about unit of measurement specification." I would think: ...


2

Yes, it's possible. Convert the known coordinates from lat-long into various coordinate systems and see what matches. Looking at a few of your lat-long values, it seems that your data is in California, so my guess would be California State Plane; this may be in meters or feet, but the conversion will tell you quickly.


2

The distortion in MODIS imagery people mostly worry about is the well known Bowtie effect due to whiskbroom scanning. The Sinusoidal projection, or Sanson-Flamsteed, is an equal area projection and thusly both tiles you mentioned cover roughly the same area and have identical pixel sizes.


2

you can use gdalbuildvrt instead of gdalmerge to create a virtual raster template (xml file) that will behave like a merged raster. then you can run gdal_translate with the -projwin option for your set of 256*256 tiles. For most of my applications, I would create a single output per face then use gdalbuildvrt for virtual tiles. Note that if you create one ...


2

I downloaded your data and had a play around in QGIS - if I choose EPSG:102022 (Africa_Albers_EAC) it looks like it lines up. Depending on your plans for this that might be close enough - obviously for real science(tm) you'll need to go back to NOAA (or the publications listed) and check. Or you could try editing the spheroid definition below. ...


1

It is defined WKID: 102039 Put this number into the ArcGIS search bar in projections and it will show up. I agree with you this will get the shape to appear as you require. It is defined in ArcGIS so you can reproject to and from unprojected NAD 83. USA_Contiguous_Albers_Equal_Area_Conic_USGS_version WKID: 102039 Authority: ESRI ...


0

Finally got an answer on github: Internally, Leaflet transforms EPSG:4326 coordinates to pixel coordinates. These pixel coordinates are the EPSG:3857 coordinates divided by a power of 2 (and then rounded). It might be possible to fetch some of these coordinates (look at methods like L.Map.latLngToLayerPoint) and then multiply stuff given the zoom ...


1

You have to do the intersection within the same CRS, so you have to reproject one layer to the other. In QGIS, you have to use Raster -> Projections -> Warp to convert the raster to WGS84. You might need to remove the LCC layer and turn OTF OFF to see them align. Check that QGIS has assigned the right CRS to the reprojected layer when loading. Save ...


1

If your data are in different CRS you have to reproject one of them. SELECT ST_Value(rast, geom) val FROM testraster5, pft_account WHERE ST_Intersects(rast, ST_Transform(geom, EPSG_YOUR_RASTER));


2

I think we can over complicate this answer. It is meters, as UTM Zones are almost always going to use meters as their unit (exceptions are so rare as to not be worth a mention). If you suspect you are using something that is not meters it will say so. Use this site as it is software independent if you must look it up. http://spatialreference.org/ Then ...


1

The unit of the projection is used for area calculation, meter or decimal degree or feet. Check Settings/Options/Crs, see screenshot:


1

I think that you should check a few items: check layer CRS check project CRS (set automatically reprojection on the fly in: Settings > Options > CRS) After open vector layer in QGIS use tool "identify Feautures" and select one feauture In "Identify Results" dock window "expand all" and look for area units Now you can use "Filed calcuator" or Vector > ...


2

Try changing the buffer method from Planar to Geodesic Arguably, in such small scale features this shouldn't change much, but stranger things have happened before. Here's a case where I buffered some points in a geographic CRS with a planar buffer of 250 meters and displayed on a projected CRS. Using a geodesic method solved this issue for me.


0

In which projection is your data? When uploading data to CartoDB with a specific projection, CartoDB transforms the geometries to EPSG 4326 and also to Web Mercator for the geometry to be visualized. Most basemaps out there represent the world by following the Web Mercator projection, which is the standard in the current web mapping world. CartoDB ...


1

From your description, I extract two properties : must fit in a rectangle (so that you can duplicate along the horizantl direction and turn around the Earth without adjusting the center of projection). This will not be the case with Robinson or Eckert must preserve areas: you don't want a huge Greenland Therefore I suggest cylindrical equal area, but ...


2

All projections change the distances, projections can preserve angles or areas only. If the distortion caused by the projection is less then 10 cm/km considered a very good projection. The real distance is very hypothetical, if you measure the slope distance between two points the slope distance will be reduced to the horizontal plane, then to the see level ...


1

You can do that from command line with ogrinfo http://www.gdal.org/ogrinfo.html and SQLite SQL dialect http://www.gdal.org/ogr_sql_sqlite.html. Example: Select state called "Colorado" from spapefile, convert geometry into EPSG:3857 and compute the area. Unit corresponds with the base unit of the projection and in this case will be square meter. ogrinfo ...


3

I would advise against using coordinates outside UTM boundaries as this can cause unforeseen problems further down the line when others use the data and may be unaware of this. I would consider it bad practice unless no other alternatives exist. This has been recognized as a problem in Idaho and a solution exists so why not use it? The Idaho Transverse ...


1

I think that it is acceptable to use one UTM zone for all for the sake of analysis. For longevity, a continental-scale projection (like Albers Equal Area in North America) would be more appropriate (especially for published data). We used to use UTM Zone 17 for all of West Virginia when I worked in WV even though the eastern panhandle is in zone 18. Same ...


4

The symbol size in QGIS refers to the size of the bounding box, not the radius. So in the case of a simple circle marker, the size refers to the diameter, not the radius. The same goes for ellipse markers. I think this might be because there are lots of types of symbol (circle, triangle, cross, SVG symbols), so treating circles differently would add ...



Top 50 recent answers are included