Questions tagged [area]

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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92
votes
5answers
207k views

Calculating polygon areas in QGIS?

How do I calculate areas of an area shapefile in square meters or in acres (ha)? I didn't find that functionality in the vector tools.
22
votes
3answers
23k views

Getting polygon areas using GeoPandas

Given a GeoPandas's GeoDataFrame containing a series of polygons, I would like to get the area in km sq of each feature in my list. This is a pretty common problem, and the usual suggested solution in ...
18
votes
6answers
26k views

Removing only donut holes from polygons using ArcGIS Desktop?

I am using ArcGIS Desktop 10.0. I have a trick for removing the donut holes, which is converting the polygon to line and then creating polygon out of the lines and in the end merging all of them. ...
18
votes
5answers
19k views

Area in KM from Polygon of coordinates

I have polygons from coordinates in (python shapely) that looks like this POLYGON ((24.8085317 46.8512821, 24.7986952 46.8574619, 24.8088238 46.8664741, 24.8155239 46.8576335, 24.8085317 46.8512821)) ...
17
votes
1answer
25k views

Calculate area within Python script in ArcMap

I am trying to calculate the area of a polygon within my Python script. I create a new polygon from merging two together, and I'd like to add the area of the resulting polygon to a field in the output ...
15
votes
2answers
16k views

Is it possible to gray out a Google Maps map except for some area?

What i am looking for is a way to emphasize a certain area on a Google Maps map by graying out the rest of the world. I heard about some solution of using 2 polygons of which 1 is visible and the ...
14
votes
5answers
21k views

How can I measure area from geographic coordinates?

If I have polygons in geographic coordinates (WGS84), how do I measure the total area each takes on the surface of the earth, taking into account the curvature of the earth?
14
votes
2answers
4k 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 ...
13
votes
2answers
43k views

How to calculate polygon areas and perimeters using QGIS?

Using QGIS, if I load a polygon layer and make a new column, how do I fill that column with the: area of each polygon and another column with length of the perimeter of each polygon?
12
votes
3answers
4k views

Calculate total area of polygons in shapefile using GDAL?

I have a shapefile in British National Grid projection: Geometry: 3D Polygon Feature Count: 5378 Extent: (9247.520209, 14785.170099) - (638149.173223, 1217788.569952) Layer SRS WKT: PROJCS["...
12
votes
1answer
11k 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 lonlat/EPSG:4326, as ...
12
votes
2answers
9k views

How does ST_Area in PostGIS work?

I am performing a simple calculation on a polygon known to be approximately 6226 km^2 in area. It is stored in a Geography (WGS84 SRID) column. The query is: select st_astext(col), st_area(col) area ...
12
votes
1answer
2k 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 antemeridian,...
11
votes
3answers
4k views

More accurate way to calculate area of rasters

In my daily work, I am constantly asked to calculate areas of global raster datasets in geographic projection at 30 arc second resolution. These datasets are normally the result of a Combine operation ...
11
votes
2answers
1k 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, it'...
11
votes
1answer
274 views

QGIS versions yielding different results on $area calculations?

When grading an exam, I discovered that QGIS 3.2 and 3.4 produce different values on computing $area over polygons. I experimented using $area and area($geometry) to check the differences between ...
10
votes
1answer
29k views

Calculate area for each polygon in R

I am working with a shapefile that has many polygons. How do I add one more field named "area_sqkm" and calculate area for each polygon in the shapefile?
10
votes
2answers
3k views

QGIS area calculation differs when on the fly CRS transformation enabled

When I open QGIS, add the layer, and calculate the areas of the shapefile via field calculator I get a different area than when I open QGIS and check "Enable on the fly CRS transformation" and ...
10
votes
3answers
11k 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 6105215....
10
votes
3answers
9k views

Splitting irregular polygon into equal areas using QGIS?

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 ...
8
votes
2answers
8k 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 ...
8
votes
1answer
537 views

Circle area calculation in QGIS is inaccurate

I created a circle with a radius of 3 km, calculated the area using field calculator and got a different result from real area. The QGIS result is 28273078.8 while manually calculated area is ...
8
votes
3answers
3k views

Remove Holes Existing Within a Single Polygon for a specific area in Qgis

I have a shapefile that consists of a single polygon. I have gaps within the polygon that needs to be eliminated, but only the ones that are less than 200m2. I tried different ways but none of them ...
8
votes
4answers
8k views

Calculating areas of different raster classes in R?

I have generated a raster as a *.tiff file in R, with four classes. I'd like to calculate the area occupied by each raster class. Each class has a value (-5, -4, -3, -2) - I expect that I could also ...
8
votes
1answer
8k views

How to measure areas of features in OpenLayers plugin background maps correctly?

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" toolbar, and i have tried fTools in ...
8
votes
3answers
3k 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 ...
8
votes
1answer
6k views

Calculating area weighted average of attribute in one layer by shape in another using ArcGIS for Desktop?

For a project I am working on I would like to intersect fire station response districts with income data to determine the median income per response district. However the borders of the layers ...
7
votes
2answers
507 views

Calculating area of newly added polygons on same layer?

I have a layer where I had 6 polygons. I then used the field calculator so I could get a column with the area of each of these polygons and I thought this would be applied to any other polygons I made ...
7
votes
3answers
2k views

Obtaining same area values provided by Census for TIGER boundaries using PostGIS functions?

In PostGIS, how can I compute the area of Census Boundaries and obtain the same results as are provided by the Census? For example, most Census Boundaries include attributes for Land Area and Water ...
7
votes
2answers
4k views

Calculating proportional area of polygon within another layer's polygon using QGIS?

I have two polygon layers, model and ntem, whose features overlap and intersect one another. I would like to calculate the proportion of the area of the model polygons which fit within each ntem ...
7
votes
1answer
948 views

Equal area projections with different area results in ArcGIS for Desktop?

Using ArcGIS, I have to calculate areas of huge polygons all over the Pacific Oceans betwwen 20N and 30S. I have been trying different Equal-areas projections (Cylindrical and sinusoidal for example) ...
7
votes
1answer
1k 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 ...
7
votes
2answers
2k views

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 ...
7
votes
1answer
645 views

Calculate or Estimate TRUE AREA from an irregular polygon and a DEM in QGIS

I have to calculate or estimate the surface area (sq m) considering the elevation data on several places (wich i have in different shapefiles, and some multipolygon shapefiles). I'm aware of this ...
7
votes
1answer
3k views

Unit of Geotools' getArea function

I have Polygons with WGS84/EPSG:4326 coordinates (like 13.57933804767844,52.5126298984133) and use the Polygon.getArea function to obtain the area of the polygon. But the result I get is something ...
7
votes
3answers
4k views

Calculating area of vegetation in 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.
7
votes
2answers
2k 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 ...
7
votes
1answer
417 views

QGIS tool to identify polygons that can fit a certain sized square within the polygon

I am trying to identify parcels with enough space for an additional building, and one of the parameters for this is: there needs to be a space of at least 9' x 10' available to fit the additional ...
7
votes
2answers
569 views

Creating a raster of percent of pixel occupied from shapefile [closed]

Starting from a polygon shapefile, How can I produce a 1km raster, where the cell values are the percentage of the pixel occupied by the shapefile. For example the values would range from 0 to 100%. I ...
6
votes
2answers
12k views

Creating a circle with radius in metres

I am using shapely and Python. How should I go about creating a circle using shapely whose radius is in meters? If i use sampleCircle = Point(1,1).buffer(1) print sampleCircle.area This returns ...
6
votes
3answers
13k views

How to recalc WGS84 Shape_Area field to square miles in ArcGIS 10

What are the units of the Shape_Area field in a wgs84 feature class? Is it decimal degree squared? I would like to convert that to something more meaningful like square miles without reprojecting the ...
6
votes
2answers
2k views

Deleting polygons smaller than certain dimension using ArcGIS Desktop?

I've made a model in ModelBuilder in ArcMap 10.3, what it basically does is creating polygons over open areas such as farm-lands, grass-lands, marshes etc that has a low slope. My challenge is that I ...
6
votes
2answers
10k views

Calculating bounding box size?

What formula could I use to calculate the size in Kilometres of a bounding box based on a given South-West latitude/longitude and a North-East latitude/longitude points? The bounding box format is ...
6
votes
1answer
211 views

$area gives NULL for some polygons in QGIS's Field Calculator

I have the map of Cambodia(map) and the economic land concessions(elc). In trying to find the proportion of district covered by land concesions, I need the area variable. But when I create the ...
6
votes
3answers
2k 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 ...
6
votes
1answer
109 views

Dividing the world space to geographic sub-space

I am trying to divide the world space to geographic sub-space from "general" to "specific" locations and without using latitude and longitude information. That is, I am trying to think about the world ...
6
votes
2answers
2k views

Wrong $area from field calculator (QGIS)

The area of the polygons in a layer, calculated by the field calculator with "$area" is wrong (much too big) for some polygons. If I draw the concerned polygon again, the area is calculated correctly. ...
6
votes
2answers
605 views

Increase each polygon area to the same area

I'm using ArcGIS Desktop 10.2. I have many polygons (buildings) with various areas and I want the same area for all my polygons: 100m². The final goal is to aggregate them and build the urban ...
6
votes
1answer
267 views

QGIS.2.18. cannot save calculated area into layer

After I calculated several areas in the attribute table (added a column, named it "Areas" and then calculated with "$area" in the calculator), I could not save the new information within my given ...
6
votes
2answers
6k views

Converting area from degrees to square kilometres using OpenLayers geometry?

I get a multypolygon from my web service and want to calculate the area of that polygon. I was trying to use this piece of code: var poly = new OpenLayers.Geometry.MultiPolygon(poligon); var area = ...

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