Hot answers tagged image
4
If you're using Python I'd recommend using the GDAL library, which has it's own Python bindings. Assuming you've got both GDAl (see this GIS StackExchange question for details on how to install on windows) and numpy installed, your code could look something like:
from osgeo import gdal
import numpy as np
#Open our original data as read only
dataset = ...
4
Though I am not able to understand the difference between the standard
deviation output and the percentage output and what is the
significance of using one over the other?
Those refer to the threshold used to decide whether there has been any change between two images. For percentage change, it uses a symmetric relative difference formula to
...
4
Of course you can change the OpenLayers default z-index.
Just overwrite the z-index default range before anything.
OpenLayers.Map.prototype.Z_INDEX_BASE.Feature = 2000;
OpenLayers.Map.prototype.Z_INDEX_BASE.Popup = 4000;
OpenLayers.Map.prototype.Z_INDEX_BASE.Control = 5000;
var map = new OpenLayers.Map();
...
3
Combined pan-sharpening, contrast stretching, and gamma stretching functions
If you have access to ArcGIS (and the Spatial Analyst Extension) you can use the technique described in this blog to "blend" DEM (or imagery) with shaded relief. The main disadvantage of this solution is that it is static; you need to produce an RGB raster from your DEM so if you ...
3
In theory, it should be possible to create one layer, add images as features with externalGraphic, and set their size (graphicWidth, graphicHeight) dynamically by context function. This will "emulate" georeferenced images.
In practice, first problem is - after changing zoom, when feature's origin is not on screen, it's not displayed. Zoom in in example, and ...
3
You have tagged your question with OpenStreetMap, so I am assuming you are interested in the data in OSM's zoom levels.
Please have a look at: Zoom Levels
Usually you would not look at the whole world, at the same zoom level, as you would a small city. Your example is at zoom level 17, which has a scale of 1:4000.
You would look at the world either at ...
3
From the USGS FAQ: the blue band is useful for "Bathymetric mapping, distinguishing soil from vegetation and deciduous from coniferous vegetation".
It's my experience that you get better results by using band combination, however.
3
GIS file formats contain georeferencing information. This ties image pixel coordinates to grid references in a projection system, in this case British National Grid.
There are lots of ways this information can be stored depending on image format. A basic tool to get you started is gdalinfo which will query the extents of the image in British National ...
2
I am not sure if this is the complete answer, but there seems to be a problem with GIF and PNG images that have transparent backgrounds not displaying or export/printing correctly in ArcGIS v9.x - 10
Here is the Knowledge Base Article: Transparent GIF and PNG inserted images do not display and/or do not export or print as transparent
It is not really clear ...
2
there are some nice JavaScript project to deal with maps (also "little" maps like yours :) ).
I recommend to take a look to Leaflet, which is a really lightweight and simple to use library (http://leaflet.cloudmade.com/)
On the other hand you have OpenLayers which is a really powerful and complete library (http://openlayers.org/).
These can help you with ...
2
Get the projection reference from the input GDALDataset:
GDALDatasetH hDS = GDALOpen("input.tif", GA_ReadOnly);
const char *pszWkt = GDALGetProjectionRef(hDS);
//make sure its not NULL
OGRSpatialReferenceH hSRS;
hSRS = OSRNewSpatialReference(pszWkt);
//create your ogr datasource, hOGRDS
//Create a layer and pass in the spatial reference.
OGRLayerH hLayer = ...
2
Something like this should work:
from os import startfile
from os.path import abspath, dirname, join
proj = QgsProject.instance()
urfile = str(proj.fileName())
path = join(abspath(dirname(urfile)), "HyperlinksTest", "[% PDF %]")
startfile(path)
You can just paste this in as in you don't need to have it all one one line.
2
Another approach that doesn't generate a new image - specially in a situation where you have a plethora of large raster datasets - but uses the existing ones could be using the gdalbuildvrt command line: it gives you more control for the output through its options and you don't need to provide the txt file with the raster list if all of your images are in a ...
2
Once we get a Satellite Image, we need to georeference it. What this means, is that we need to modify and recitify the image and set a lat long (or X Y Coordinate in general) for each pixel of the image.
This is usually done, by setting the lat-longs for known points on the image(Just as you have done). But to actually modify the image, so that it becomes ...
1
Yes, your example seems logical, however I think you mean georeference not geocode. To start this setup you can do the following:
Create a new polygon feature class defined with a spatial reference (in meters) that matches your geographic area of interest.
Load in your polygon layer into ArcMap and start an edit session on it.
Zoom in on the map to the ...
1
I found that it was simply the size of the image/map i was trying to print/create.
On a side note: I have moved from using the export to PDF button in favour of using file>print> and selecting print to pdf. In this I can adjust the quality of the drawing to high (600dpi) and still create a smaller file size and the risk of crashing has been significantly ...
1
I guess same as with writing to PDF, if the image is very large:
http://osgeo-org.1560.n6.nabble.com/qgis-and-Large-Format-Print-td5016300.html
Try the QGIS Master available by OSGEO4W installer (qgis-dev package). Maybe the problem is fixed there already.
1
You can add a symbol to the map rather than the print output in Composer.
QGIS 1.8.0 Lisboa has some generic symbols included. If you go to Settings/Style Manager then ADD then Symbol Layer Type and choose SVG Marker you can choose from a number of symbols there and save the one you want.
Once you have your chosen symbol you need to add a Shapefile Layer in ...
1
This is more of a comment, but it is hard to format code in the comments...
With the OGR Python bindings, I write out a .prj file after outputting the shapefile. Note the MorphToESRI() function to translate the SRS WKT to ESRI's flavor. In the code below, latlong is a OSR SpatialReference object.
# write a .prj file for our shapefile
...
1
Just do:
wget http://mysite.com/mapserv.cgi?map=../../mapfiles/demo.map&layer=land&mode=map&FORMAT=image/png
You are getting some wget log output in your image file. See the manual for other information about how wget works.
1
In ArcGIS you can apply a hillshade effect to a DEM - it's a check box on the Symbology tab under Properties.
This will allow you to keep the values in the DEM, but still allow for the visual effect of the hillshade.
1
You could 'merge' dem and hillshade. You could add 1 (grayscale or colormap) or 3 (rgb) bands to the dem. I don't see any benefit to doing so, and it would probably cause confusion given 2 band images are rare and 4 band images will likely at some point be misinterpreted as and RGBA image. Personally, I wouldn't do it.
1
I suppose it depends on how you want to have it display. If you want to show more detail as you zoom in (kind of like the maps from the Rumsey Map Collection do on Google Earth-- I believe that Google calls it a SuperOverlay), I'd recommend using something like MapTiler (http://www.maptiler.org/), which uses GDAL to split your image into tiles of different ...
1
Perhaps you could use Time Album for that purpose (software and manual)?
It's a small Java program designed to work with Columbus gps loggers and works with data in CSV format. It has a function to link pictures to gps tracks and export as KML. I'm not sure though if CSV data must be supplied in Columbus specified format but perhaps you could reorganize ...
1
I use the following code:
graphic = new OpenLayers.Layer.Image(
'Viewshed',
'http://..../image.png',
new OpenLayers.Bounds(20.008697509767,32.076110839844,20.123138427735,32.154235839844),
new OpenLayers.Size(750, 512),
{ isBaseLayer: false,
opacity: 0.3,
...
1
GeoRSS is used in that example because Flickr providing geotagged images through a GeoRSS API.
There are several solutions here, but I recon that most of them require you to write some OpenLayers code, and unless you use a photo storing site such as Flickr, you would have to write your own mechanisms for storing and retriewing your images as well.
A tip ...
1
You need to make a getfeatureinfo request and then display the result in a popup. The basics of this are shown in this example. Once you have this working with your data you will want to format the information returned by the getfeatureinfo request so that it displays the image GeoServer provides a templating language that will allow you to do this - see ...
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