Hot answers tagged overlay
19
You are confusing two different operations dealing with Projections.
Define a projection: You would use this when you have a shapefile or other featureclass, that does not currently have a spatial reference defined when you look at the properties in ArcGIS. You might also use this if you knew based on some observation, that the projection defined for the ...
10
Here is how I would do it in a Desktop.
Get Quantum GIS Desktop, an Open Source and popular GIS
Desktop.
Install Openlayers Plugin(In Menu, Plugins -> Fetch Python
Plugins would display the plugin)
Set Project CRS to EPSG:3857
Add Bing/Google Satellite Layer( Plugins -> OpenLayers -> Add Bing/Google)
Add PostGis Layer(Layer -> Add Postgis ...
9
These are the basic steps you need to run through (is this what you have done? Apologies if this is too basic)...
Make sure that your 1940 shapefile has an attribute containing county
area (e.g. ‘Area1940’)
use the Union tool (ArcToolbox > Analysis Tools > Overlay > Union)
with your 1880 and 1940 shapefiles as inputs.
Specify a new output shapefile.
In the ...
7
This is a graph coloring problem.
Recall that a graph coloring is an assignment of a color to the vertices of a graph in such a way that no two vertices which share an edge will also have the same color. Specifically, the (abstract) vertices of the graph are the polygons. Two vertices are connected with an (undirected) edge whenever they intersect (as ...
6
It's not possible to mix geometry types in layers.
You will need to add separate layers.
Also, I'd recommend splitting the layers by topic, e.g. one layer with buildings, one with general zoning info. Don't just throw everything into one layer, otherwise you will have a mess to clean up later. Also styling is going to be easier with more layers.
As @Willy ...
5
I would recommend clipping the raster to the shapefile, then in the resulting raster you can look at the number of cells present for each of your classes. The area can be calculated by multiplying the number of cells by the area covered each pixel (cell size squared).
It's a different approach than the equally valid solution offered above but from a ...
4
Here is working code:
options = {
div: "map",
zoom: 5,
center: [-10796366.372312, 4426748.6429884],
layers: [
new OpenLayers.Layer.OSM()
],
projection: "EPSG:3857"
};
map = new OpenLayers.Map(options);
var noaaRdr = new OpenLayers.Layer.WMS(
"Latest Radar",
"http://nowcoast.noaa.gov/wms/com.esri.wms.Esrimap/obs?",
...
4
This a simple tutorial one can follow to define/transform geographic coordinate system and/or datum in ArcGIs 9.3., starting from a ".csv" file.
Open ArcMap;
In ArcMap, click on “Tools” button located in Main Menu. Choose the
following option: “Add XY Data”;
On “Add XY Data” window, click at the browse button to open the
“.csv” file which contains ...
3
I recently performed a similar task, where I converted a series of 3D polygon shapefiles into KML files to view the data in Google Earth. I came across the Export to KML extension for ArcMap 9.3 or 10, which handles the export of shapefiles as KML, allowing labels, styles, temporal data and attributes to all be set and modified. I have found this extension ...
3
This can be accomplished using three main steps:
Convert your raster to polygons using the Raster To Polygon tool
Overlay your polygons (from raster) with your shapefile using the Intersect tool or Union tool - which depends on how many polygons you want output
Tabulate your results using the Summary Statistics tool (or perhaps the Tabulate Intersections ...
3
What you are describing can be accomplished using Extract by Mask. For example, the image on the left shows raster imagery with a polygon overlay. The image to the right shows the result of the extract by mask operation. By default, ArcGIS assigns NoData pixels as no-color. For display purposes, I reassigned the NoData pixel color from no-color to black ...
3
The methodology recommended by #whuber inspired me to take a new direction, and here is my arcpy solution, in two functions. The first, called countOverlaps, make two fields, "overlaps" and "ovlpCount" to record for each poly which polys overlapped with it, and how many overlaps occurred. The second function, explodeOverlaps, creates a third field, "expl", ...
3
This is documented here. In short, you can add a WMS layer within your mapfile as follows:
LAYER
NAME "country_bounds"
TYPE RASTER
STATUS ON
CONNECTION "http://demo.mapserver.org/cgi-bin/wms?"
CONNECTIONTYPE WMS
METADATA
"wms_srs" "EPSG:4326"
"wms_name" "country_bounds"
...
3
To continue webrian's suggestion:
v.select ain=poly_a b_in=poly_b oper=within out=a_within_b
Now the output vector "a_within_b" will contain those polygons from a that were totally within b.
But be careful: when you import a shapefile into GRASS with overlapping polygons, the overlaps will be split up by the topology "clean" operation, so you'll have ...
2
As @drnextgis states the displayProjection property of the map is only really about the system in which coordinate values are displayed to users (behind the scenes I think OpenLayers is doing a transform).
When you add an OSM layer to the map it becomes the base layer, it is the base layer that then informs the projection of the map. So, since OpenStreetMap ...
2
Assuming that your code is correct (I have given the value 1 for the cs variable), the error it gives is:
Error in function (classes, fdef, mtable) : unable to find an inherited method for function ‘over’ for signature ‘"SpatialGrid", "SpatialPoints"’
According to the help file, this is what the function is waiting as input:
x: geometry (locations) of ...
2
If the two datasets are showing up in the same area in ArcMap it's likely they have projections defined, allowing ArcMap to reproject on the fly. Because they're not exactly over the top of each other its likely that the original sources are different, which can potentially make things a bit more difficult.
I'm assuming that the classifications don't line ...
2
I would suggest you to do a thin buffer for the boundaries or the coastline, until one layer completely covers another. Then you can use Split tool to split the coastline according to administrative areas, and then Spatial join tool to attach to the administrative areas the corresponding pieces of the coastline.
And firstly to better match the layer you can ...
2
Andreas Hocevar has created an OpenLayers branch (currently in the pull-request queue) that solves this problem.
Rather than using the SelectFeature control, the branch enables the employment of event listeners that do not get in the way of other event intentions such as panning the map while inside one of your vector layers.
Your code may look ...
2
You can use groups in order to turn a set of layers on and off together. Just CTRL+click the layers you want in a group, right click one of them and select "Group". The layers will remain separate entities but you can turn them all on or off at once rather than manually finding the layers you need for a given scenario.
1
I can't point to an app that currently does this, but you should see more apps supporting this type of feature soon due to the new Android Maps API V2 that came out a few weeks ago.
Android Maps V2 directly supports a "GroundOverlay", which is an image overlaid on the map:
...
1
I would suggest that you think about meeting your requirements with a slightly different approach.
MapServer can cascade WMS services, but I am not aware of any public WMS services that serve up OSM data for free. Most OSM data services that I am aware of use the tiled TMS specification.
If your version of MapServer is compiled with a version of GDAL ...
1
EDITED after feedback from question poster.
Step 1: if files are not georeferenced, try the methods described here,
georeferencing using gdal tools.
Also world files could work for weither png or tif (http://en.wikipedia.org/wiki/World_file; http://www.gdal.org/gdal_translate.html).
Step 2: two methods could work for the clipping. Trying gdaltranslate ...
1
If you have clean topographic map (that means that bulidings have the same colour, not different shades) it is the easiest thing to do reclassification (1-buildings, 0-everything else). Then you can rasterize your polygon file showing new buildings (be careful and use the same resolution, width and height as your topo map so they will match). Then you can ...
1
I think what you are describing is known as coplanar polygons - shapefiles are more likely to keep two polygons in separate "planes", i.e. no intersections created, but the Union tool can be used to planarize them.
1
I recommend using Map to KML in ArcMap 10. Labeling the features is not straightforward--although, there is a good discussion here.
Begin by creating the map overlay you would like in ArcMap,
including colored outlines, opacity, etc.
Run Feature to Point
Turn on the labels in your new point layer
Save the map as a .mxd
Run Map to KML (Define the output ...
1
I suspect, have not had a chance to test, that this may be the relevant part of Union help to read:
"Attribute values from the input feature classes will be copied to the output feature class. However, if the input is a layer or layers created by the Make Feature Layer tool and a field's Use Ratio Policy is checked, then a ratio of the input attribute value ...
1
First, do a union of the two shapefiles. Then select just the private lands from the union shapefile. Summarize on CountyName, click the plus sign next to SHP_Area and choose "Sum". This should give you a table that shows the total area of private lands per county.
Select just public lands and then summarize again to get the total area of public lands ...
1
If your diagrams represent values from polygons, here's what I do:
Create a new shapefile of centroids ("Vector->Geoprocessing Tools->Polygon Centroids"). This is a point layer with all the data columns from the original polygon. Now edit this point layer, and move the points to wherever you want each chart. And finally recreate the charts from this point ...
1
If I understand your question correctly, instead of intersecting the buffer and the output area classification layers, what you really needed to do was a spatial join using the buffer layer as your base. This function will then automatically calculate statistics (you have a choice of statistics) concerning the parts of the area classification layer that fall ...
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