Area is a quantity that expresses the extent of a two-dimensional surface or shape, or planar lamina, in the plane.

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3
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2answers
758 views

How to calculate the area of rasters in QGIS?

I have been working with some rasters and would like to know how to calculate the area occupied by one element of a raster in Qgis.
3
votes
1answer
1k views

Calculate polygon area inside extent

We're using ArcMap 10.0 sp5, creating a tool in c# using the ArcObjects sdk. Is there a built in function or simple set of steps that calculates the area of each feature of a polygon layer within a ...
4
votes
1answer
286 views

The number of digit of decimal point when you calculate area of polygon in QGIS1.8.0

I would like to change the number of digit of decimal point when I calculate area. For example Now: 32.456677 Ideal: 32.46 I try to adjust "output field width" and "Precision" These don't work well. ...
3
votes
3answers
766 views

Auto-calculate field (area or formula)

I'm wondering if anyone has any insight into the potential to auto-calculate the value of a field, either area or distance (ideally) or a formula (based on the values of say 2 other fields, or an ...
5
votes
3answers
377 views

Polygonize vegetation area from Landsat7 RGB using QGis / Bilko?

I'm trying to extract the areas with vegetation as a polygon-shape from a landsat7-image, 30m resolution, RGB, using QGis 1.8 or Bilko or (hopefully in the near future) ArcGIS. The area is in Northern ...
0
votes
1answer
423 views

Which area measurement to trust? - The same polygon in GoogleEarth v. ArcGIS [duplicate]

Possible Duplicate: What is the most accurate coordinate system for calculating areas of polygons? I'm currently involved in comparing the "official metropolitan" areas of several cities ...
3
votes
0answers
240 views

Getting coordinates of pixels

I want to compute an area of certain object on a picture using Monte Carlo method. The picture shows some shape on white background. To do so I figured out that I'd get the coordinates of non-white ...
6
votes
1answer
426 views

QGIS define hexagon area around mapped points

I am using QGIS to map a number of radio antennas (for mobile network). Once I have the layer of the sites (done), I would like to assign to each site a coverage area (envelope). I could achieve that ...
1
vote
1answer
877 views

How to use field calculator for area calculations in QGis? [duplicate]

Possible Duplicate: Calculate area between contour lines on a DEM with Qgis 1.8.0-Lisboa Based on a DEM of a whole country I have reclassified altitudinal bands with steps of 100 metres ...
3
votes
1answer
213 views

PostGIS: worldwide area calculation

I have a table with polygons in EPSG 4326. These polygons are distributed all over the world, for example: POLYGON((10.7324632658845 59.9253049236956,10.7331908150806 ...
6
votes
3answers
2k views

How do I get the area of a WGS84 polygon in square meters?

The following gives me the area of the polygon in square degrees: SELECT ST_Area(ST_GeomFromText('POLYGON((871325.790874952 6105405.3261047,871418.748307692 6105359.72944624,871346.22022442 ...
6
votes
1answer
680 views

How to calculate te area between contour lines on a DEM with Qgis 1.8?

Does anyone know how to calculate the area in km² for each altitudinal band (between 100 and 200, 200 and 300...) based on a DEM? I added the contour lines with a distance of 100 metres but could not ...
1
vote
0answers
30 views

area weighted average for overlapping polygons [duplicate]

Possible Duplicate: How to use NASS county level crop data to estimate crop acreage in hydrologic regions? It seems like an easy problem but I don't know how to go about it. I have two ...
7
votes
2answers
2k views

How to split an irregular polygon into equal areas?

I am a surveyor and use QGIS for maintaining soil test records on civil projects and am constantly provided with test lot area or number of lots required. These are more often than not irregular in ...
3
votes
2answers
243 views

Determine density or cover from a raster layer that has been clipped by a polygon

I am a very new GIS user using ArcMap 10. I have a raster layer of tree canopy that I have clipped so that the layer is in a polygon that is a circle with a 2km radius. I have done this for four ...
6
votes
1answer
193 views

How do I represent the whole Earth as a Polygon?

This is related to determining the interior of a Polygon. My difficulty is that if I specify a Polygon covering the Earth going from East to West, it will still have a boundary along the ...
6
votes
2answers
256 views

How do different GIS systems determine a Polygon's interior?

I'm interested in understanding how real-world GIS systems and their data encode Polygons. Specifically, how do they resolve the ambiguity of a Polygon's interior on a sphere? Background: in 2D, ...
1
vote
1answer
101 views

Transform csv-coordinates into area

I'm working with an inventory of a species in Southern Sweden. I have recorded my findings (together with coordinates, name of the species and year of finding) and created a CSV-file with i have ...
4
votes
4answers
370 views

How to compute geodesic area in GeoDjango?

I have some polygons which can be anywhere in the world. I would like to compute their areas. The GeoDjango docs for GEOSGeometry.area don't specify whether it is geometric or geodesic area, but ...
5
votes
2answers
657 views

PostGIS - area-weighted calculation on an intersection

I'm trying to learn postgis sql by performing some familiar operations from ArcGIS. Here, I want to perform an area-weighted calculation of certain populations on the intersection of a set of parcels ...
8
votes
3answers
852 views

calculate area of vegetations in a raster file

How do I calculate area of several vegetation types in a raster (.img file type) image. They are color coded. Am using QGIS (1.8.0) and ERDAS 9.2.
6
votes
2answers
653 views

How to get correct area calculation using Google Mercator?

i use QGIS with openlayers-plugin and i´ve loaded google satellite as a layer. what i want to do is making a shape-layer (polygon) with the goal to get the area values of the polygons. i´ve activated ...
6
votes
1answer
2k views

How to measure area correctly?

I have now used my entire evening, but I can't figure out how to make areal calculations (eg. in km2). I have tried the 'field calculator', I have tried the 'measure area' function on the "attributes" ...
2
votes
2answers
431 views

How to single out country data from a world data map?

Say that i have two "data sources"; A global map of average wind speeds, A shape file (or similar information) of all country borders in the world. How do i combine these two sources and extract ...
1
vote
1answer
227 views

Summarize polygon area using another polygon

I have a shapefile representing public/private lands in Montana. This is a multipart shapefile where I've simplified attributes so that #1==private and #0==public. Next I have a shapefile of ...
1
vote
1answer
338 views

ESRI android SDK Calculate area in square meters from polygon geometry

Hello I have a Polygon object in ESRI Android SDK that I'm creating on a map, I would like to calculate that polygon object to square meters. currently I use double area=polygon.calculateArea2D(); ...
3
votes
1answer
954 views

How can I get my Qgis area calculations in metres rather than degrees? My shapefiles are projected using WGS 1984 UTM fuseau 35 Sud

I am using Qgis 1.7.4 to calculate the area of polygons. My shapefiles have been projected using the coordinate system WGS 1984 UTM fuseau 35 Sud, but my area calculations are still displayed in ...
2
votes
0answers
108 views

GeoTools, add column in query with CQL

I'm trying to query the database (DataStore) and want to let the datastore calculate a value for me. In SQL I would do it like this: SELECT name, ST_Area(ST_Intersection(the_geom, ....) AS myValue ...
2
votes
0answers
699 views

How to calculate the area of a polygon considering the relief?

I work in a fire department and i'm mapping all the fires that occur in my area, creating polygons that represent burnt areas. my problem is that the values are not accurate... for instance, arcgis ...
3
votes
1answer
278 views

How to calculate buffer surface that falls within another layer's borders

The image below shows what two selected layers. One contains a series of borders, and the other a series of buffers. I am trying to obtain the buffered surface within each of the borders in the ...
5
votes
2answers
6k views

How to calculate polygon areas and perimeters?

If I load a polygon layer and make a new column, how do I fill that column with the 1) area of each polygon and another column with 2) the length of the perimeter of each polygon?
4
votes
2answers
865 views

How to calculate area of 1 x 1 degree cells in a raster

I have a simple array (not geo-referenced in any way) in Matlab (which is not a language I know a huge amount about...so I can export it to other languages if needed) which has the dimensions 180 x ...
4
votes
2answers
716 views

Why does ST_Area(g.geom) + ST_Area(p.geom) - ST_Area(ST_Union(g.geom,p.geom)) produce negative result when using ST_Overlaps(g.geom, p.geom) = true?

I have two set of shape data. Let's say file gov.shp contains list of post codes and their boundaries. File post.shp contains list of government area name and their boundaries. I want to find out the ...
-1
votes
1answer
227 views

Finding the area of a polygon feature in a shapefile [closed]

Excuse the very simple question. How do i find the area of a selected polygon feature in a shapefile?
1
vote
3answers
519 views

How to calculate forest area of a bitmap (jpeg) map?

I have a map of 1:50,000 scale map in .jpg format. Can i calculate the land area of forest,lakes etc from arcmap.Anybody can give me the step to do it? And I want to know what is the coordinate ...
2
votes
1answer
1k views

Convert area from square meters to degrees globally

I have a global raster file with 3600x1800 pixels. I don't have any information about the projection used. The raster contains one band with a quantity with the unit "per square meter". How can I ...
6
votes
2answers
275 views

Projections appropriate for global analysis that preserve area and that preserve distance (but not necessarily in the same projection)

I am looking for a projection (or a set of projections) that decently preserve distances so that I can buffer every country in the world and have a similar level of minimal distortion for each. I ...
2
votes
3answers
287 views

How to calculate exact area of a loaded jpg map in to arcmap?

I calculated the polygon area through arcmap.but i'm not sure that the area is not actual,may be scale is not right. so how to calculate the exact area of a jpg image?
2
votes
1answer
2k views

Calculating area of an EPSG:4326 Polygon [duplicate]

Possible Duplicate: What is the most accurate coordinate system for calculating areas of polygons? In our Postgres/Postgis database we store polygons in a column defined as ...
1
vote
1answer
292 views

How can the scale be projected correctly in Quantum GIS when it is imported from google earth (KML) files?

While importing KML files from google Earth to Quantum GIS, the scale is not being projected properly and the area of a particular selected feature is not being calculated in the attribute table by ...
1
vote
1answer
2k views

Measuring on OpenLayers map

These days, I am trying to develop web map using openlayers. I copy source code from here Then I changed code to display my data.B ut it does not work, even map is also not showing. In chrome shows ...
1
vote
1answer
559 views

How to color markers based on polygon area?

I have a map with around 317 markers and each marker is the center point of a polygon. The polygonal area varies throughout, so I want to represent the markers in such a way that the polygon with the ...
3
votes
1answer
189 views

km2 or sqkm - which is more correct?

What is more correct, km2 or sqkm? I'd prefer to use km with a superscript 2, but it's not always possible to format text that way so I was just wondering if there is a convention that should be ...
1
vote
1answer
389 views

The units of getArea() on a multipolygon within a shapefile [closed]

I am using GeoTools to find area and intersections of shapefiles. GeoTools uses the JTS geometry library (Vivid Solutions) and that has functions to getArea() but unfortunately I am not able to ...
5
votes
2answers
976 views

Shapefiles for U.S. Area Codes (NANP)

I have a bunch of telephone numbers (just the area codes), and I'd like to geolocate them and make a map, but I haven't had too much luck googling for shapefiles for Area Codes. Surely these are in ...
2
votes
1answer
174 views

Converting 2D shapefile to Equal Area Projection?

I have thousands of shapefiles with coordinates in lat/long (-180 to +180 x, -90 to +90 y), that contain polygons of which I wish to calculate the area. I'm using the Python GEOS/OGR/GDAL API. If I ...
2
votes
1answer
475 views

Why does intersect not calculate polygon areas?

this is strange: I intersected 2 shape-files and the resulting shape does not contain the Shape_Area and Shape_Length of the intersected polygons. Instead the field Shape_Area contains the ...
4
votes
1answer
2k views

How to display Radius after Resizing a Feature in Openlayers

@captDragon has helped me with calling the coordinates of a polygon after I have resized or dragged the feature. Ineed the radius now, i have done a radius alert on my other map,Which works correctly, ...
0
votes
1answer
696 views

how do i calculate polygon area with arcobjects?

i'd like to develope an application with arcengine that can calculate area of a polygon . i wrote the below code to select a polygon in combobox for (int i = 0; i < pmapcontrol2.LayerCount; ...
0
votes
1answer
403 views

how to calculate polygon area in arcengine

i'm new to use Arcengine 9.3 . i would like to create an application to calculate the selected polygon in combobox such that the user click to a button and polygon area saved in dbf . how can i write ...