Tagged Questions

Raster is a data format consisting of regular grids of values, usually stored in an image-like format.

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0
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1answer
377 views

NDVI image value

In order to get monthly NDVI image with max value from two 16 day-images, I used mosaick tool in ERDAS8.7 by choosing max function from "set overlap function" tool. But after doing this, when I see ...
2
votes
1answer
447 views

Why won't this simple raster layer in my mapfile show up?

I am trying to get a simple raster layer to work on MapServer. I am not exactly going to be using geographic data, but I want to "georeference" multiple rasters together to create a map-like ...
3
votes
5answers
1k views

When a raster is clipped to a polygon with Python, why does it still take on the extent of the entire shapefile?

I am clipping a raster image to each polygon row in a shapefile in ArcMap 9.3 using the Clip tool (Data Management) in Python with Clipping Geometry set. While the clipped raster successfully depicts ...
3
votes
4answers
1k views

How to clip raster image by the extent of each row in a shapefile with ArcGIS 9.3

I'm using Python to clip a raster image by each row in a shapefile with ArcGIS 9.3. I am hoping to end up with one raster image for each polygon row, clipped to the extent of the polygon row. ...
13
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4answers
502 views

When should I be calling a 'rectangular grid of pixels' a raster or an image?

Reading through GIS literature, it sometimes feels that authors use the two terms with a specific meaning in mind. I always treat the terms interchangeably. Am I wrong? Read the first line in the ...
3
votes
2answers
727 views

Overlaying GPX data on rasters in QGIS

I have a series of raster map images that I would like to use in QGIS and overlay some simple GPX routes over the top to produce a custom map image. This is all quite new to me so please bare with ...
21
votes
3answers
4k views

What is Lanczos resampling useful for in a spatial context?

GDAL includes a resampling method beyond the normal mix of nearest neighbor, bilinear, cubic and splines: "Lanczos windowed sinc resampling". I understand that its a convolution filter, but unlike ...
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1answer
130 views

Clip GAPAnalysis and save as a new file output strange looking colors

I download USGS GAP Analysis and use a polygon to clip raster from that GAP Analysis. I am wondering why there is a strange looking color when you clipped the raster. If you zoom in, you can see ...
5
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2answers
612 views

BBOX and Projections of WMS services in Geoserver

we have tried to overlay a raster layer on Google map and have some difficulties to align the raster images onto the base map. When it is on the overview (Zoom level 1), it looks like this: On a ...
2
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4answers
519 views

Extraction of monthly image from two-16 day images

I need to conbine two-16 day NDVI image into monthly NDVI image. To do this, what kind of function and formula are used in ENVI, ARCGIS or ERDAS? Best regards,
5
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3answers
2k views

resize image resolution from 1000 m to 250 m

I'm beginner of ARCGIS and RS. I have many problems with the procedure. One of them is I have NDVI images and Soil map. Both are at the different resolution: NDVI is 250 m. soil map is 1000 m. So I ...
2
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1answer
416 views

How can you make RasterToASCII_conversion observe environment setting output cell size?

I have two rasters (an ESRI grid and an IMAGINE image) that differ in projection, extent and cell size. I want to convert the IMAGINE to an ASCII, and want it to have the extent, cell size and ...
1
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0answers
641 views

Conversion to Raster issue in ArcGIS 9.3.1

Trying to convert a polygon to raster in ArcGIS gives me an error... I am wondering if there is another way around to do this? I am using ArcGIS 9.3.1. The error i am getting is number 9999 when I ...
20
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3answers
17k views

How to clip a raster with vector boundaries?

I am using QGIS. I would like to clip a raster precipitation layer using an admin boundary layer that is vector data. However the geoprocessing tools seem to be usable only for vector data. How can ...
4
votes
2answers
1k views

Calculating Net Primary Production (NPP)?

When I calculate Net primary production (NPP) for a local scale, what kind of software should I use? I always use ENVI, ERDAS IMAGINE, ArcGIS for Desktop and IDRISI. Is it possible to use these ...
3
votes
1answer
698 views

Solar radiation calculation from GTOP030 DEM image

Can you help me to calculate solar radiation from GTOPO30 DEM image at the 30 m spatial resolution. I'm trying to do this many times using spatial analysis solar radiation calculation tool in ArcGIS. ...
3
votes
1answer
292 views

About FAPAR calculation

I want to calculate FAPAR in different land cover types using max and min value of NDVI. I have a raster image with 9 Land cover types and max, min value of NDVI in each land cover type. But I don't ...
7
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3answers
3k views

Simple Question: Raster from ArcGIS to Geoserver

we have a couple raster files which could be open in ArcGIS. They come with the extension of .aux and .rrd and they are the GRID file format from ESRI. We want to put them on Geoserver to overlay them ...
4
votes
2answers
1k views

Translating grid to USGS .dem in C# via GDAL

I am attempting to translate ArcInfo binary grids to USGS DEM format (.dem). I have installed the GDAL .NET bindings thru this build installer. I can get to GDAL in my C# add-in I am working on. ...
2
votes
1answer
90 views

Can the concentration of values in a raster map be known?

I have a generated raster map containing different flood levels. Is there a grass script to determine the percentage of values in a raster map? I'm thinking of using r.mapcalc to solve this, but I'm ...
2
votes
2answers
821 views

Interpolating heights in DEM using ArcGIS API's in C#

I am new to ArcGIS and not familiar with it. I want to interpolate heights in a DEM file using ArcGIS? Is it possible? Actually, I want to write a C# code that will read the height from DEM file for ...
8
votes
4answers
381 views

Identify corrupt shapefiles or rasters via Python or ArcObjects

I'm interested in a way to identify rasters (e.g., ESRI GRID format) or shapefiles that are corrupt that would prevent them from being used in an analysis tool. I have a large number in structured ...
3
votes
2answers
944 views

Fastest way to create an ESRI Grid and populate cell values?

In terms of processing speed what's the fastest way of creating and then adding values to a raster? The values will originally come from ASCII files which can be about 500MB in size - ideally I ...
24
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4answers
8k views

What raster smoothing/generalization tools are available?

I have a DEM that I would like to smooth or generalize to remove topographic extremes (chop off peaks and fill-in valleys). Ideally, I would also like to have control over the radius or level of ...
6
votes
3answers
5k views

Finding nearest raster cell value based on vector point?

I have two layers in ArcGIS: One is a vector point and the other is a raster layer. I want to append the value of the raster data grid to the vector point. The problem is the vector point is away from ...
5
votes
1answer
321 views

Unknown Coordinate System on old drawing

I work with many old civil engineering documents, and occasionally I'll need to georeference one which has coordinates pairs listed at many given points but does not list which coordinate system these ...
6
votes
3answers
838 views

Converting point data into a weighted raster

I am completely re-writing my question as i think it was quite confusing before: I have a number of different points, each point has a -z value. I need to create some sort of raster or a series of ...
6
votes
2answers
1k views

Creating shapefile of satellite image footprints?

I'm looking for a tool or a workflow to compute satellite image footprints, for a large number of images across directories, and produce a shapefile. Ideal work flow would be: fire up tool point to ...
4
votes
1answer
851 views

Can QGIS resample Rasters during display?

When I was using ArcGIS a user could resample a raster during the display (I think via layer properties under the display tab). This would smooth the appearance of the raster so it wouldn't appear ...
6
votes
1answer
585 views

In QGIS, how do I remove a band from a raster?

When I process a raster in QGIS it creates a second band. It appears that band has no useful data. I like to use the Raster Colours Tool and it will not accept a raster with anything more than on ...
11
votes
2answers
507 views

How sensitive is Landsat to atmospheric correction?

How important is it to correct Landsat for atmosphere, haze and convert DN to reflectance? What impact does it have on the results, say for many of the vegetation indices?
3
votes
2answers
921 views

Change output file type in QGIS georeferencer?

I have successfully georeferenced a raster file via the Georeferencer plugin (Georeferencer GDAL Version 3.1.9) in QGIS 1.7.0. However, I noticed that the output georeferenced raster file is in TIFF ...
7
votes
2answers
3k views

Modify raster layer display and symbology properties programmatically with arcpy or ArcObjects

I have over 1500 NITF files that I need to be able to modify the layer display and symbology of programmatically from within ArcMap. I need to set the properties outlined in red below: I've looked ...
2
votes
1answer
622 views

GeoTIFF raster layer, c#

We have a map rendering engine (renders from MapInfo Interchange Format). This engine uses Mercator Projection. Now we have to insert a raster layer (orthophotos of a city), we have GeoTIFF files with ...
3
votes
1answer
410 views

Taudem Resources

As I frequently deal with hydrology, I've heard Taudem mentioned quite a few times. I'm finding all sorts of information, but much of it is dated for use with previous versions. In addition, the ...
4
votes
1answer
807 views

How can I calculate the vertical distance to the nearest water?

Summary: I would like to create a raster where each cell contains the vertical distance to the nearest water (a decent approximation would be acceptable). The problem is that I'm not sure how to go ...
3
votes
3answers
712 views

Overlay polygons on raster colour map to extract area values for each colour within each polygon

Does anyone know an answer to the following: I have a set of polygons created as the MCP of animal movements. I also have a habitat colour map raster, with 13 different habitat types as different ...
5
votes
6answers
6k views

How Do You Remove No Data From A Raster (.sid)?

I have an Image.sid that has a white border which is No Data. I've tried using Clip Raster Tool with no success. I've also changed the symbology value for No Data to be transparent. I'd like to ...
6
votes
1answer
422 views

QGIS composer - How can I eliminate striping across transparent raster layers?

I have downloaded QGIS dev version 1.7.0-114 and I have come across some weird behaviour in the composer. I create a map with a hillshade and a transparent DEM ontop of it, pretty standard stuff. ...
6
votes
5answers
1k views

Is there a way to clip an image with the basic ArcView package (9.3)?

Is there a way to trim a geo-referenced air photo to an irregularly shaped boundary? I tried the clip tool shown in my attachment, but it didn't work. It looks as though the output extent field ...
2
votes
3answers
251 views

Trying to make the private land white overlay hillshade but

I'd like to have anyone's feedback on this draft map I created. Tried to make the private ownership white but since it's RGB is not near to 255. I've seen someone created this map similiar to it and ...
1
vote
2answers
3k views

Remove overlap in raster using ERASE command line?

I am trying to erase a raster and is there a erase command for the Raster side? I am using ArcGIS 9.3.1. I have 2 rasters that are in the Landcover and there is overlap in between and would like to ...
4
votes
3answers
697 views

Australian Topo Map GeoTIFFs

Does anyone know if Australian topo map GeoTIFFs are made available anywhere (preferably for free)? LINZ makes them available in New Zealand - http://www.linz.govt.nz/topography/topo-maps/index.aspx ...
5
votes
2answers
4k views

Convert x, y position in georeferenced image (with world file) to longitude, latitude?

What steps do I need to do in order to calculate longitude and latitude for a specific pixel in a georeferenced image? For example this image ...
6
votes
1answer
677 views

Is there a way to get the percentage of different landuse types upstream of a given point?

I'm a fairly novice GIS user and know just enough to get in trouble in a lot of cases. I am trying to look at the connection between several measured parameters at a few hundred stations along ...
1
vote
3answers
531 views

Point to Raster Issues

I am having some trouble with something fairly simple.. I am creating a 3D subsoil model for display in arcscene - i can get it displayed nicely as points but in order for the model to be easier to ...
3
votes
1answer
838 views

Cropping an image with a map extent

I have an raster file in my server space, which has the same projection as my webmap, and I would like to crop the image by passing the visible extent of a webmap. I think the cropping function is ...
1
vote
2answers
219 views

Setting Rasters to the exact same display

I have been tasked to make a series of .jpeg outputs of different sections of a dike displaying elevation data. My problem is that the data i have been given is GIGANTIC, almost the whole region made ...
0
votes
1answer
646 views

ArcGIS Desktop 10.0 — layout Data Frame Grid color inversion on export or print when other rasters are active

Having a problem with ArcMap 10.0 SP1 Data Frame Grid of graticule inverting color on export or when printing. Occuring on multiple classroom PCs all working with the same datasets. Exporting to ...
3
votes
2answers
1k views

JPG file all black when added as raster in QGIS

I add a new raster layer in the latest QGIS and select a JPG file, but it is all black. I tried adding the TIF version of the same image and that worked. What is it with the JPG, and how should I ...