New answers tagged projection
0
I found the solution, "divide and conquer". After I cut the image in small pieces, they aligned correctly with google and my other layers. As I supposed from the beginning, this problem is because this big raster crosses two UTM zones (17 and 18 south), and the normal stretching must occur close to the Equator (its northern edge gets up to 5ºS). Thus, ...
2
For a complete history of the evolution from EPSG:900913 to EPSG 3785 and finally EPSG:3857, look at Análisis de Google Maps (in Spanish) and the conclusions are:
The projection parameters defined for the EPSG: 900913 or 3785 describe a Mercator projection with geographic coordinates defined on a spherical model of the Earth, 6378.137m ratio, as specified ...
1
The Google Mercator projection is usually bound for aereas between 85.0511° North and South.
If your data includes 90° North or South, the reprojection is mathematically not possible.
See also http://wiki.openstreetmap.org/wiki/Slippy_map_tilenames for all kinds of lat/lon to Google Mercator conversions.
0
You could use the ITransform2D interface, it has a scale method.
2
Copy the polygon.
Normalize the polygon by subtracting the center values from every point.
Scale the normalized polygon in the manner you describe.
Add the center values back to every point.
If the data is in lat/lon, you may get better results if you first project it (to any planar system you like) then scale as I've described then deproject.
1
The openlayers plugin requires EPSG:3857 Pseudo Mercator, because that is the CRS the tiles from Google or Openstreetmap are delivered in. The CRS has units called metres, although they are real metres only at the aequator.
It is not a good idea to switch from that CRS to another, because then all tiles will be reprojected individually, leading to nasty ...
1
Firstly you are using the wrong tool to project the data.
Secondly, the area and lengths calculated from geometry usually don't match the official statistics. This is because of a variety of reasons including :
The actual area on the ground is measured taking the terrain onto account.
The way the official area is calculated, introduces many systematic ...
3
One of the strange Limitations of ArcMap, is that it only looks at the name of the projection, and doesn't actually check the parameters, if the name is different.
I've often faced this problem when data comes from other software. That software might use the correct parameters for say UTM 43N, but the name is not what ArcGIS expects. And all ArcMap can do, ...
2
Think of projection as seeing your location on X/Y plane.
Datum defines the reference point from where all measurements were made. Say you are located somewhere and need to tell your location to someone. You would say, i am X lat and Y long. This X and Y are deterministic because they are being referred from the Datum. The other person now knows that you are ...
1
Others have already given valid answers depending on what it is exactly you need. For whats it is worth, you could reproject both data sets to Transverse Mercator with a custom central meridian that lies directly on the mid-line between the two. Or, if you are working with data in high northerly latitudes you could simply reproject both to Lambert Conformal ...
0
As mentioned in the above post, assign GCS "WGS 84" to your ArcGIS map document for best result.
0
If you are planning on showing a grid on top of your map, Radar's suggestions would suit the situation. If you don't need to show any grid, I would just leave the projection as geographicals WGS84.
Additionally here is the link to Esri's Help 10.1 on the issue. Crossing map projection zones
1
If you're just looking at displaying the data and since neighboring zones have some overlap (1 degree), you may consider reprojecting the zone with the least amount of data - pending there isn't too much of a spread. Note that is there is too much spread this method will introduce distortion which could affect areal calculations.
Alternatively, since your ...
1
I can spot two things:
Change every instance of EPSG:900913 to EPSG:3857 -- EPSG:900913 (Or EPSG:GOOGLE if you squint hard enough) never existed in the EPSG database. It's a long story, but EPSG:3857 is the correct code.
It looks like you have one too many zeroes when you initialize your minLat and minLong variables. Compare it to your new ...
0
It is best to use a combination of both.
Humanly understandable location descriptions are for humans and geographic coordinates can be left to computer software.
Racks, bays and tiers in warehouse shelving systems are normally indexed in a humanly understandable and memorable way such as numerically, alphabetically and/or by colour codes and so on. Items ...
0
Thank you for your responses, I managed to solve my problem.
I projected the dem using the "Project raster" tool and my shapefiles using the "Project" tool in ED50 UTM 35N. I saved the project and closed ArcMap, then opened an empty ArcMap and imported the transformed raster so that the coordinates are displayed within the new coordinate system.I ran my ...
0
If most uses of values will be by a map application, storing values on geographic( geocodes as you typed ) will save you from the conversion cost each time you need it on map.
You can save both local and geographic values so the map has his data ready, and another application that use another coordinate space can use the local values.
Local coordinates ...
2
I think, technically, this 'question' should be split into several questions! I going to try to answer your questions or clarify your statements out of order because I think it will make more sense.
A coordinate reference system, when used in the GIS field, is a generic term for a reference framework that's used to locate points (lines, polygons, etc). ...
1
You can find a shapefile (vector) for countries as of 2010 from
http://epp.eurostat.ec.europa.eu. It think that it would be easier to change the symbology of a vector file than deal with a raster. Arcmap will project on the fly and you can set the map to a winkel projection (projected->world or world-sphere->winkel).
2
Try just setting project CRS and enabling on-the-fly reprojection. Don't touch the layer properties. If the Shapefile .prj definitions are read correctly by QGIS, that's all you need to do.
Similar questions:
Why don't my Shapefiles and OSM data overlap in Quantum GIS?
QGIS layers no longer overlay when Enable 'on the fly' CRS transformation ...
0
Just a comment on the diagram that is trying to illustrate a projection from a sphere. Rather that what is illustrated, imagine a light source at the center of the sphere. The shadow of the polygon "projected" onto a flat piece of paper outside of the sphere is in essence a type of projection. To me the diagram is implying a projection is like a reflected ...
1
A map served by Geoserver as EPSG:4326 and displayed in OpenLayers with this "projection" will look distorted. The units of measure in a EPSG:4326 is degrees, so what you are looking at are an unprojected map.
You'll want to make Geoserver reproject your WMS to eiter EPSG:900913 (or whatever EPSG-code "web/spherical mercator" has nowdays) or a local system ...
0
If you're working with the local ellipsoid then it's a better distance approximation than the pythagorean distance, reason for that (in my knowledge) is quite simple : ellipsoid is meant to be a better approximation to distances. So unless you're working with a non-local ellipsoid, it's the way to go.
0
This link may be helpful to you, it mentions a pitfall that projects your coordinates into the wrong location:
The Impossible Made Possible: Projecting Greek Data into UTM
0
ESRI:102100 isn't WGS84 (EPSG:4326), but "WGS 1984 Web Mercator". The Mercator projection is conformal (maintains shapes) just like tranverse Mercator which is what British National Grid uses. However, it's generic for the entire world, while BNG's parameters have been customized for Britain, Scotland, and Wales to minimize distortions.
I am not surprised ...
3
It's true that Google uses Google Mercator (EPSG:3857 or EPSG:900913) for displaying, but I think you/the Javascript API want lat/lon coordinates for input.
So convert the data into EPSG:4326, and look if it fits.
You can load the shapefile into QGIS, and use Openlayers plugin with Google or Openstreetmap background to check if the transformation is ...
4
Load the shapefile 'as is' into QGIS and Save as KML will do the conversion and will show correctly in Google Earth.
See:
http://pvanb.wordpress.com/2012/07/31/exporting-vector-layer-as-kml-in-qgis/
for Google Maps you need to upload the kml to a public facing webserver.
Example Layer in Google Maps API v3
...
2
Google uses Google Mercator projection. EPSG:900913. For proj4 settings see here.
To display your data in Google Mercator:
On QGIS status bar click on the grey globe icon to open the Project Properties page. Check Enable 'on the fly' CRS transformation and select Google Mercator -EPSG 900913 and click Apply.
To save data in Google Mercator:
Right click on ...
1
In the end I decided to avoid the issue by making my OL layers multitiled (singleTile: false) with the appropriate maxExtent to prevent requests outside of the appropriate area. This way, since my layers are around Hawaii and never actually cross the date line, I won't have issues with OL making bad requests with respect to the IDL.
The only downside is ...
0
No that's not possible.
If you describe your workflow, we might be able to suggest an alternative.
0
Here's one for Arc that goes through several scenarios using vector data:
http://blog.geographyforever.org/2013/03/25/working-with-spatial-reference-systems-in-arcgis/
1
Many different tools implement conversions between tile z/x/y and bounding boxes for a given projection. This problem is not specific to Mapnik at all. Why not use a library like TileStache, Invar, or MapProxy?
2
I do not know of any automatic projection algorithm or software that could master so many challanges and unknown parameters in one picture (extremely high panorama-induced distortion in the NW direction, unknown look angle and flight height of the sensor, unequal pixel size, interrupting elements in the picture and many, many others). The only thing you ...
2
I'm asuming you are talking of how GIS softwares show data with Lat Long on a Flat map, like this:
Al the GIS Software that I have worked with, inlcuding ArcGIS & Qgis, treat the latlong as linear units, and show the data in pseudo Plate Carree projection.
Now that I think of it, this question seems an exact duplicate of How is EPSG:4326 data ...
0
To overlay the custom WMS layer correctly, I would first set the projection of the map, by passing in the projection parameter, and then at the end I would set the bounds in this projection.
My code would be as follows:
function init() {
var webMercator=new OpenLayers.Projection("EPSG:3857");
var wgs84=new OpenLayers.Projection("EPSG:4326");
var ...
1
Although I have found no documentation to the effect that a Projected Coordinate System is required it is perhaps unsurprising that a Geographic Coordinate System is unsupported because the length of a degree varies depending on the latitude.
I suspect that a documentation enhancement is the most that is likely to happen with this but I encourage you to ...
1
perhaps it is (lack of) datum transformation in the projection operation? Your symptom sounds familiar. It is a common problem here in WI - GPS uses the WGS84 datum, but our state system uses NAD83HARN. The symptom of doing a projection without datum transformation is that coordinates are systematically offset a few meters in X and ~meter in Y.
3
The answer is Yes.
Have a look at this sample: Generalized Data.
If you have a look at the Original Services, the Feature service is wkid:4267, while the map and the tiled map service are in wkid:3857/102100.
If you have a look at the service call using Firebug, you will see that the data is requested in wkid 102100:
1
The provider either doesn't know or doesn't wish to include a complete coordinate reference system definition in the metadata. The provider has given you the ellipsoid (spheroid) and prime meridian only. Unless you can find out somewhere else, there's no way to know what the GeoCRS and datum should be.
Usually, Clarke 1866 means a NAD 1927 datum. However, ...
0
The datum is not part of the original Shapefile .prj definition, and ESRI do not incorporate any datum information into their .prj files. They handle datum definitions seperately, but do not save them in the shapefile.
QGIS does it, but creates also a .qpj file which feeds the need of datum shift definitions.
EDIT:
If the projection is in degrees, a prime ...
1
After finding this comment, I searched for this spatial_ref_sys table and inserted it into to my PostGIS database.
Reloaded the shapefiles into PostGIS in ESPG: 900913.
Restarted TileMill, added my PostGIS layers, and they are all layered correctly.
0
You should use the following code:
var wfs = new OpenLayers.Layer.Vector("WFS", {
strategies: [new OpenLayers.Strategy.BBOX({resFactor: 1})],
projection: new OpenLayers.Projection("ESPG:28992"),
protocol: new OpenLayers.Protocol.WFS({
url: geoserverURL,
srsName: "EPSG:28992", ...
Top 50 recent answers are included
