A map projection is any method of representing the surface of a sphere or other three-dimensional body on a plane
1
vote
1answer
33 views
Why do points shift when reprojected from WGS84 to a state plane coordinate?
We have a Trimble unit we use to collect equipment.
We collect the data in WGS84 and differentially correct it and then reproject it to a state plan coordinate system.
The points always shift the ...
1
vote
0answers
45 views
QGIS: Different projection result for on the fly and transformation
I am a bit confused about the result of a re-projection/transformation of a raster in QGIS 1.8 (Lisboa).
WGS84 to WGS84/UTM34N. When I use the 'on the fly' transformation the resulting raster has a ...
0
votes
0answers
19 views
De facto QGIS projection for EPSG4326 / 'unprojected' reference systems? [duplicate]
This is my understanding of projections/datums:
To get a map of the earth on a plane you need to project the 3 dimensional earth by 'wrapping' a plane around it in the way that suits you (according ...
2
votes
1answer
33 views
Do FeatureLayers reproject their features to adapt them to the map projection?
I'm working with the ArcGIS Flex API.
For example, ArcGISDynamicMapLayers do reproject their data in order to make it in the same projection as the map.
Do FeatureLayers have the same behaviour?
0
votes
0answers
21 views
QGIS: Unable to project raster layers correctly on a Toshiba Tecra 64# Win7
I know how to project a raster, I can do it on other machines. On this particular machine the raster loads but are no where near the correct position as if the datum is on another planet.
9
votes
0answers
68 views
Assign projection to a satellite image
Today I stumbled upon a picture taken from the ISS looking down Europe and it is really beautiful.
So, I started thinking I could add more to the picture. Like world borders, cities, road network, ...
1
vote
2answers
37 views
define a datum and meridian in a CRS in QGIS
I have a shapefile defined by the source as:
"The layer is in geographical (lat-long) coordinates (GCS_Clarke_1866; Datum: D_Clarke_1866; Prime Meridian: 0)."
opening the shapefile in QGIS 1.8 the ...
1
vote
1answer
30 views
Incorrectly Projected PostGIS data in TileMill
When I bring PostGIS data in EPSG:900913 into TileMill, my layers end up on other continents.
This is my workflow:
(1) Save shapefiles in QGIS to EPSG:900913
(2) Import the shapefiles using PostGIS ...
0
votes
1answer
29 views
Wrong projection on WFS layer with OSM baselayer [duplicate]
I am trying to add a vector layer with a WFS protocol.
var wfs = new OpenLayers.Layer.Vector("WFS", {
strategies: [new OpenLayers.Strategy.BBOX({resFactor: 1})],
...
2
votes
1answer
119 views
What are the units of the calculated area from a raster in decimal degree
I'm trying to calculate area for a raster file which contains 2 layers (0 for unsuitable habitat and 1 for suitable). It's been calculated successfully but I don't know what is the unit of the ...
1
vote
0answers
22 views
how to get correct geo reference system for a VMap
I am new to GIS, trying to read the GeoRef System for VMap by using the following code:
OGRSpatialReference *ref = layer->GetSpatialRef();
if( ref )
{
QString georefSystem = ...
1
vote
0answers
16 views
Projection issue: mismatching .shp even if with the same SCR
I have a problem with some .shp from ARCgis (point and polygone) that appear on QGIS with mismatching SRC. When I change and save the new SRC (even by doing "save as") to make them match nothing ...
12
votes
2answers
152 views
What is the approximate error of the Pythagorean Theorem vs. Haversine Formula in measuring distances on a sphere at various scales?
Many people when first trying to calculate distances between two longitude / latitude pairs ask if Pythagorean theorem works as an appropriate distance function.
Most often people answer "no, the ...
0
votes
0answers
38 views
How to get Earth radius in pixels?
I need Earth radius in pixels for use in Mercator projection. Well let's say that our map's height is 1478 pixels and distance between 0 pixel and 1478 pixel is 2.52 degree. Radius is distance from ...
3
votes
1answer
62 views
Compute global DEM topographic indices and compromise projections
I would like to compute global topographic indices based on SRTM elevation data. These indices are computed along river/channel networks extracted from a DEM and are a functions of both local slope ...
1
vote
1answer
58 views
openlayers multiple layers with different projection
My page contains two layers: 1. Open Street Map as a basic layer and WMS layer from mapserver as a overlay layer. My map show this two layers but in a wrong position. I spent a lot of time trying ...
3
votes
1answer
52 views
What is displayed when I am using a geographic CRS for my project
I understand that each geographical dataset has a CRS, and that in order to overlay them, you need to either make sure that all datasets use the same CRS, or re-project some of them (or use on-the-fly ...
6
votes
2answers
69 views
IDW spatial interpolation: appropriate projection?
I am wondering if anyone can clarify whether point data should be projected to an equidistant projection when using ArcGIS IDW spatial interpolation?
I am working on a dataset from Western North ...
0
votes
1answer
39 views
OpenLayers WMS - TypeError: this.resolutions is undefined
I'm trying to setup a map with WMS and WFS Layers by using Geoserver.
However, when I'm combining WFS and WMS (with some Google basemaps) together in one map I got following error in Firebug:
...
0
votes
0answers
30 views
I want to change EPSG:4326 to EPSG:900913 using C# for a set of uploaded shapefiles
I have written some code (using help from these pages) that uploads a directory full of shapefiles to a geoserver using C#. The uploaded shapefiles are set to EPSG:4326 however I would like them to be ...
0
votes
0answers
34 views
Reprojecting raster data from a rotated pole grid
I have some raster data (ASCII grid files) that use a custom rotated-pole projection, that I'd like to reproject into something more useful, such as lon/lat WGS84. A description of the grid projection ...
0
votes
2answers
54 views
WFS reprojection problems
In geoserver i have a layer in EPSG:4326.
In OpenLayers i add it on map as WFS:
markerLayer = new OpenLayers.Layer.Vector('Markers',{
strategies: [new OpenLayers.Strategy.BBOX()],
...
0
votes
1answer
37 views
Imported GPS data does not overlap with map
I´m working on QGIS and I geocoded 2 addresses of a city in Germany and tried to input the text-file as a layer. It worked, but the 2 points must be in the map of the city and if I zoom to the ...
2
votes
1answer
35 views
Transformation of user-defined projected coordinatesystems
I want to transform from one projected coordinate system (pcs) to another using ArcGIS 10. Unfortunatelly the starting system is not predefind by ESRI and thus I´m not sure the software is doing what ...
2
votes
1answer
39 views
Ok to measure and union a projected-on-the-fly shapefile in ArcMap?
I have a dataframe in arcMap 10.0.4 that is of Africa Albers Equal Area Conic PCS. I bring in a census shapefile of WGS 1984 CS and it is projected on the fly.
I do 2 things:
I use the calculate ...
0
votes
2answers
59 views
Getting a “square” of lat/lon for database query [duplicate]
So I want to get the square formed by a single point of lat/lons, my plan was to take that point's latitude, divide by 360, and multiply by the circumference of earth. Giving us the distance from the ...
0
votes
0answers
43 views
GMT raster (*.tiff + *.pgw) in epsg4326 shifts few kms (4326-900913-3857 problem?)
This seems to be an old problem with an already known solution (ie. "...stop using 900913 and start using 3857..."), but not sure whether this problem is about software versions, the raster itself or ...
9
votes
2answers
238 views
How do I perform a 3 parameter geotransformation and projection in Sql Server 2012?
I have a table with latitude longitude (NAD27) columns in it. I compute two other columns, X and Y, representing Web Mercator (WGS84) location.
Currently I'm using a Arcmap to do this, by applying ...
2
votes
1answer
64 views
Find projection of a point to a line
I have a segment defined by 2 LatLon points(A and B) and a third LatLon point (C).
I need an alghorithm, formulae, or some code to find the projection point of C on the segment AB (call this point D) ...
1
vote
3answers
39 views
Trying to match delimited text layer to my shapefile
I'm pretty new to QGIS and having a bit of trouble getting a text layer to match my shapefile. I'm trying to plot Canadian cities on a shapefile I have of Canada provinces.
The provinces shapefile is ...
0
votes
0answers
48 views
Shapefiles with EPSG 31467 and 3044 don't fit together [closed]
I have a problem with some shapefiles I want to fit in my exisiting project. My project layers use as CRS EPSG 3044. They do fit together with OpenLayers GE (EPSG 3857). Now I wanted to add some new ...
0
votes
0answers
36 views
How to join edge of International Date Line in world file?
I am currently using world file (http://www.ngdc.noaa.gov/mgg/shorelines/gshhs.html) for international boundary information.
Now I have difficulty with map projection that the map ends with ...
1
vote
1answer
60 views
Data points Imported into QGIS are in the middle of ocean
I'm new to QGIS and tried importing some GTFS data in the CSV format (stops.txt). The project CRS, base map CRS and GTFS CRS have all been set to Google Mercator, but the points that are supposed to ...
1
vote
2answers
57 views
Get Lon Lat values from a GEOGRAPHY data type in PostGIS
After storing lon lat values as a GEOGRAPHY data type, how do I retrieve the individual lat lon values?
Failed attempt:
SELECT id, geog, ST_X(geog), ST_Y(geog) FROM locations;
Error:
No function ...
1
vote
0answers
35 views
Determining the SRID of a dataset in PostGIS [duplicate]
Sometimes the dataset provides some information about its projection. For example, it can mention Horizontal_Datum_Name: North American Datum of 1983, Ellipsoid_Name: GRS1980, ...
1
vote
2answers
125 views
What Spatial Reference System do I store Google Map's Lat/Lng in
I am new to PostGIS, Spatial Reference Systems and projections and want to store lat/lng coordinates retrieved from Google Maps and Openstreetmap and its services like the Geocoder/Nominatim. I'm ...
3
votes
1answer
65 views
What's the difference between Geographic coordinate system 4019 and 4121?
I have a DEM with cell size 100,100 with geographic coordinate system GRS_1980_Transverse_Mercator, Datum: D_GRS_1980. I created some extra shapefiles with projected coordinate system: Greek_grid, ...
2
votes
2answers
56 views
What's the correct transformation for Lambert Conformal Conic for Wyoming?
I am a newb in QGIS. I have loaded QGIS 1.8 (Lisboa) and practicing with a number of maps for portions of the state of Wyoming. My maps are mostly in UTM 12N NAD 27 & NAD 83 some are in decimal ...
0
votes
0answers
34 views
include the robinson projection into open layers
I need to include a robinson projection into openlayers, but i found no epsg code for it.
i have this spherical mercator projection at the moment and need to change it, but i dont know if it is ...
2
votes
1answer
83 views
Correct coordinate systems, but trustworthy distance between points?
I have limited GIS experience with projections and I have some questions about trying to accurately display point data from two different sources in ArcGIS 10.1 in order to do a proximity analysis.
...
0
votes
2answers
45 views
How do I reproject one raster to match another's in GRASS
I have two raster layers, A and B, which have information about the same location but have different projections and datums.
How can I reproject layer A to match the projection and datum of layer B?
...
2
votes
1answer
91 views
QPJ files on ESRI software
We have some GIS data, which was converted from AutoCAD dwg to TAB using mapinfo, then converted to shapefiles as that's what we are required to create. Editing the data fields was done in the shape ...
2
votes
0answers
22 views
Projection string for GOES-WEST
Full-res, full-disk GOES-WEST images are available from
goes.gsfc.nasa.gov. Is it possible to rig up a projection
string for these images?
We know the center pixel is at (0N, 135W) and the
satellite ...
0
votes
4answers
138 views
Coordinates conversion doubt
In QGIS do I have a EPSG:4326 shapefile that shows the coordinates "-7148300 -3688500" and I need them in the format -64º -31º for further processing in a geodjango app.
However using ogrinfo I get ...
0
votes
3answers
195 views
How can I get the proj4 string or EPSG code from a shapefile .prj file?
I have to work with a shapefile defined in an unusual projection, which my GIS software does not know about. How can I get the proj4 definition or the EPSG code for the projection?
0
votes
0answers
15 views
How to use Mercator projection on png map [duplicate]
I´ve got map(png) with size 2143x1723. When i want to get WGS84 coordinates to each point i use following algorithm
for (int i = 0; i < pictureBox.Image.Height; i++)
{
// ...
3
votes
1answer
49 views
Which Geographic Transformation to use for WGS_84 to D_Sphere?
I have a shapefile for world countries and I want to reproject it from GCS_WGS_1984 to Sphere_Eckert IV. However, it asks for Geographic Transformation; it says this is optional but it is required in ...
1
vote
0answers
40 views
How to import multiple shapefiles each with different source projections to postgis
I have a couple thousand .zip files each with a .shp, .dbf, .shx, and .prj inside them that I want to load into postgis. The problem is, they have many different source projections (each defined in ...
0
votes
0answers
54 views
Reprojecting coordinates and geoJSON in leaflet
I have a Leaflet map in default projection and a wms layer also in default (web mercator) projection. I would like to add polylines and a geoJSON layer to my map, but the coordinates are in EPSG4326. ...
0
votes
0answers
67 views
Why do ArcGIS Area Calculations not match Official Statistics?
I am trying to calculate area of polygons using a shapefile from the world bank where countries are defined.
When however I am trying to calcuate the area, the numbers that emerge are different from ...
