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1

Try to copy your shapefile into a new one with ogr2ogr and see if that helps. This QGIS issue is about phantom features http://hub.qgis.org/issues/11007. However, the problems described in the ticket appeared when opening shapefiles which were saved by QGIS with another program and not with QGIS itself. It will not hurt to try, though.


4

The "Phantom" feature likely is an invalid one, you should try to make valid it. To fix the feature you can: use the Check Geometry tool (Vector->Geometry tools->Check Geometry Validity). This allows you to find invalid geometries. In this case you have to fix the feature manually by editing it. use the Processing LWGEOM plugin: ...


0

In order to render this as a polygon, you need to enclose the coordinates in an additional pair of square brackets: lr = new ol.geom.Polygon([[ [aoi.west, aoi.north], [aoi.east, aoi.north], [aoi.west, aoi.south], [aoi.east, aoi.south] ]]).transform("EPSG:4326", "EPSG:900913")


2

In GRASS GIS, you can use r.thin for this task: The code implements the thinning algorithm described in "Analysis of Thinning Algorithms Using Mathematical Morphology" by Ben-Kwei Jang and Ronlad T. Chin in Transactions on Pattern Analysis and Machine Intelligence, vol. 12, No. 6, June 1990, along with further subsequent improvements. In QGIS, you can ...


1

With ArcGIS Spatial analyst, you can use the "thin" tool. Their algorithm is described in Zhan, Cixiang, 1993, A Hybrid Line Thinning Approach, Proceedings Auto-Carto 11, Minneapolis , pp. 396-405 As a remark, if you are interested in the process, you can also have a look at the skeletonization process in mathematical morphology. I don't know about a ...


0

I would suggest taking a look at the ArcScan toolbar if you are using ArcGIS. It has a range of functions in addition to Raster vectorisation which I think should help. Specifically the Raster Cleanup tools such as erosion and dilation which will make your lines thinner. Also check out raster snapping as that may also be useful. The image below is from the ...


1

You should provide more details about the task. In general, extracting features from the data image heavily depends on what you are trying to detect/classify, and how are you trying to do it. Here's an example. If you are interested in classifying roads from an urban scene, you may be interested in evaluating large linear filter responses over the whole ...


1

To answer your question about grabbing the layer from a clicked feature, you can do the following: map.on(ol.MapBrowserEvent.EventType.SINGLECLICK, function (e) { map.forEachFeatureAtPixel(e.pixel, function (feature, layer) { ... }); }


3

Feature extraction is not always a necessity: it depends on the algorithm used for the classification. Having too many features will lead to the so-called "curse of dimensonnality". A maximum likelihood classifier will be very sensitive to this, while a SVM classifier should in theory handle a large number of features without too much problem. Other ...


6

Take an agricultural field as a simple example. Unless we're interested in precision agriculture, in which case characterizing the variability within the field is important, then we're more likely just interested in knowing that the patch of land designated by that field is being used to grow soy, or corn, or whatever crop. That is, from an information ...


0

my strategy (very resource intensive) is to listen to mousemove and constantly saving x and y values in global variables. var mouseLat, mouseLon; function init(){ ... map.events.register("mousemove", map, function(e) { var position = this.events.getMousePosition(e); var lonlat = map.getLonLatFromPixel(position); var lonlatTransf = ...


0

Use the ModifyFeature control. Add your layer to the control, add the control to the map, activate the control and then call selectFeature() on the control and pass it your feature. The API makes it sound like you have to be in standalone mode but it works for me without being in standalone mode. I'm using OL 2.13.1.


0

I solved it myself. To hide the icon: set the externalGraphic to null. To be able to show the correct icon again I had to assign a new attribute to the feature, with info of the original icon (in my case just a code word, retrieved from the checkbox ID). To show the icon again: check if it is null, and if so set the correct icon with the icon attribute. The ...


0

OpenLayers3 ol.interction.Draw has a type property where you can restrict the type of features you can draw on a given layer. With this restriction, you can check the type of the first feature of a layer before allow editing.


0

I have just had a quick play using the developer tools in chrome to apply display:none to hide a feature, by changing it to display:inherit, the feature reappeared. I suggest you try using: var feature = pois.features; for (var i = 0; i < feature.length; i++) { if (feature[i].style.externalGraphic == "url to icon") { ...


5

A spectral signature is some measurable quantity (e.g., reflectivity, emissivity), which varies as a function of wavelength and can be used to identify a material. To obtain a signature, the quantity must be measured at a sufficient number of wavelengths (and at fine enough spectral resolution) such that the material can be discriminated from other ...


7

The term spectral signature refers to the relationship between the wavelength (or frequency) of electromagnetic radiation and the reflectance of the surface. The signature is affected by several things including the material composition and structure. Some parts of the EMR spectrum, such as the microwave region, are more sensitive to surface structure than ...


0

You are encapsulating your pois in a function using var, hence it's not possible to access it directly (search JavaScript scope on a search engine) You can always access at your demo page the pois features indirectly because map is global and layers are attached to map with map.layers[1].features Clearly, it's not safe to use an indice [1] as it may change ...


2

Doing a Spatial Join is probably the easiest... There is probably a more effecient way of doing this, but this should work... you'll need to check the field names for the WHERE clause in the MakeFeatureLayer part Notice that I used forward slashes instead of back slashes... this is not a typo... this works on Windows (even though it doesn't look right) and ...


0

In ArcGIS, you can perform a spatial join on the polygon feature class (right click on the layer >> "Join >> Join data from another layer based on the spatial location" choosing the third option "Each polygon will be given attributes on the layer that fall inside....". Then, opening the attribute table, all the records that do not have a joined data are the ...



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