The process of sorting or arranging entities into groups or categories; on a map, the process of representing members of a group by the same symbol, usually defined in a legend.

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4
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1answer
2k views

How to train a signature file for supervised classification in ArcGIS 9.3

I wanna do supervised classification in ArcGIS 9.3. I have a 321RGB composite of a pretty good quality which I want to use for supervised classification. How can I create signature file which contains ...
3
votes
1answer
163 views

Convex Hull in SAGA Gis

How does one go about creating a convex hull from a set of points in SAGA GIS? I read that this is possible in QGIS, but I prefer SAGA and would like to see if it is possible. Furthermore, if it is ...
1
vote
1answer
753 views

How to merge different classes/clusters in one single raster in arcgis 9.3?

I've created a signature file with 8 clusters and performed an unsupervised classification. Later I have grouped values (spatial) classes together to form 4 classes I needed (in symbology) but that ...
2
votes
2answers
2k views

How to classify/style rasters correctly?

I am using a GeoTiff raster data and trying to classify it. I was wondering what are the techniques that I can use in QGIS to do this? The raster I have looks like but I tried the reclassify tool ...
3
votes
2answers
257 views

calculate coastline at risk

I have an idea of what I want to do but I don't know yet what tools will bring me there. I have administrative boundaries in one layer and coastline in another layer. The coastline is categorized in ...
1
vote
0answers
89 views

From classified image to topology in ArcInfo

I have some coastal 4 band imagery that I have classified to designate land, water, and undetermined. I want to convert this to polygons with topology, and significantly simplify the polygons. If I ...
1
vote
1answer
153 views

Symbology for specific values

I want to apply a symbology scheme for the final layer of my model. Rules are - All negative - Symbol A 0 - Symbol B All positive symbol C unknown - symbol D I am not sure how I can define these ...
6
votes
0answers
393 views

Land Classification with Spectral Python (SPy) [closed]

Does anyone have experience working with the Spectral Python module for land classification? The following k-means clustering example takes an iterative approach to classification through pixel ...
3
votes
1answer
350 views

Cloud and Snow Differentiation

I am doing unsupervised classification of a mountaneous terrain and I have used 500 classes to classify the land use. In my result, cloud and the snow are categorized in the same class. How do I ...
2
votes
2answers
1k views

How to vectorize a Raster-Classification? (qgis, grass)

I classified my raster-DHM into elevation levels using colormap. Its not a "real" classification, just a colormap. So I cant vectorize the classes to get polygones for every class. Whats the best ...
4
votes
3answers
632 views

Remote sensing: How to define landuse from remote sensing data?

I am trying to research ways into obtaining landuse data for a project which calculates the visual impacts of wind parks. I have a DEM and DOPs for a relatively large region (5000km²), but I have no ...
2
votes
1answer
1k views

How to automatically export multiple maps with quantile symbology?

I am a relatively new ArcGIS user and I have a question about automating a tedious join/symbology classification/export operation. I have a very simple shapefile to which I join a bunch of fields. I ...
8
votes
1answer
2k views

Open software tool or QGIS plug-in to make land cover classification

Is there any tool or plugin for QGIS/GRASS to make an automatic land cover classification from satellite imagery --- based on CLC nomenclature for example? Of course, it will not be 100% sure but it ...
7
votes
1answer
2k views

Permanently Change ArcMap's “Maximum Sample Size” Setting?

I've lately been working on feature classes with a huge number of polygons (e.g. all of the Census blocks within the Chicago metro area). I've been needing to symbolize them by quantities a fair ...
2
votes
2answers
231 views

How to remove roads from dataset

I've got a shape file that I loaded into PostGIS that has both road and parcel multipolygons and I need to remove the roads. I tried loading the shp file in qgis and it loads them both as a single ...
0
votes
1answer
158 views

Problem running i.gensigset in Grass. Any ideas?

It just returns ERROR: Unable to create signature file. It doesn't say why... Anyone had this before and found a solution?
13
votes
6answers
2k views

Freeware alternatives to eCognition?

Does anyone know any good freeware alternatives to eCognition? I need to do image segmentation and classification. I tryed the ecognition trial and it was really good. I'm doing the job with SPRING, ...
3
votes
1answer
377 views

Standard Colors for Landcover Maps

I have classified Landsat images into five classes - A variety of Palm, Water bodies, built-up/open area, other vegetation and miscellaneous. I used GRASS GIS for the process and the final classified ...
7
votes
1answer
185 views

View data of a particular year in Google Earth

For my region in India, Google Earth tiles belong to different years, 2003 - 2010. I don't mean GE's historical view feature but the imagery updates for different areas my region. I classify Landsat ...
6
votes
3answers
178 views

Best practices for identifying training sites

Prior to image classification, collection of training sites and obtaining a signature file is the most critical step. Field visits with a reliable GPS Unit is usually the first step followed by ...
4
votes
2answers
3k views

Reclass for vector data in ArcGIS

I've got a vector dataset (in fact, OS MasterMap data) and I want to set the value of a certain field based on the value of another field. For example: Field1 Field2 Building 20 Grass ...
10
votes
3answers
3k views

Land Cover Feature Extraction from Satellite Imagery

I'm interested in a low-cost or open source solution for creating land cover GIS layers that utilize both spectral and textural extraction algorithms. I have used PCI Geomatica, ENVI, and Feature ...
1
vote
1answer
245 views

Creating color table file in PCI Geomatica

What is the simplest way to create a stand-alone color-table file in PCI Geomatica (PCT or STR)? I have some classified imagery with values ranging between 0-255 and I would like a way to ...
10
votes
6answers
1k views

What is this “brown spot” in Google maps?

I was in Google maps today and noticed near Baltimore, US where the river is, there's a huge brown spot. Is this due to all of the waste? If so, will this keep going all the way into the ocean?
19
votes
9answers
4k views

Which Tools do you use for Classification of Remote Sensing Data?

Which tool do you prefer to use for classification of remote sensing data, e.g. classifying land use, and why? Which other tools have you tried, and why did you decide against them?