Geographic Information Systems

Questions tagged [area]

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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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Converting a classification raster to a polygon, in order to calculate the area of each land use

I have 6 land use categories. ultimately I would like to calculate the area of all of the classification categories in my layer e.g. the area of the deforestation, or the area of primary forest. I am ...
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How to performing selection by expression using QGIS

I am using QGIS 3.8. I have a grid (hexagon) and a set of points. I am trying to select the hexagons containing at least 1 point. So far nothing complicated. Except that sometimes my points overlap 2 ...
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Finding areas for each polygon in multipolygon layer - CRS issues - QGIS [duplicate]

I have a layer of townlands - this is Ireland - so within that polygon layer are the various smaller townland polygons. I wished to calculate the area of each townland into an attribute I had created, ...
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There is Change in classification total area after Exporting and reclassifying it from **Google Earth Engine** to ArcMap

I have done classification of 6 classes in google earth engine on an available forest mask that has an area of about 2493 sq. km. The forest mask basically uploaded to Google Earth Engine and ...
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Intersecting geometry sum - sharing the boundary count as intersection

This question stems from Calculating proportion of area covered by another layer - not just the intersection I have narrowed down the problem. I am attempting to find the percent of district layer(...
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28 views

Calculating the area covered by isochrones in QGIS

I created isochrones using Iso-Area algorithm as polygons in QGIS. Is there any tool in QGIS that helps with calculating areas covered by created polygons?
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Find area of both sides [duplicate]

[![enter image description here][1]][1] [1]: Find area https://i.stack.imgur.com/Af6da.jpg https://i.stack.imgur.com/Af6da.jpg
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1answer
114 views

Calculating proportion of area covered by another layer - not just the intersection

This is a follow up question from $area gives NULL for some polygons in QGIS's Field Calculator and $area is NULL for over-wrapping geometry. I have a map of Cambodia at district level (dist) and ...
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$area is NULL for over-wrapping geometry

This question follows from $area gives NULL for some polygons in QGIS's Field Calculator. New question asks the same question as to why some area variables appear NULL. But the problem was resolved ...
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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 ...
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2answers
103 views

Using the field calculator to calculate intersections

I'm comparing several maps of one area (made by different people) to each other, and used intersection to find how much of specific selected features (polygons) overlapped. I soon realised that the ...
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GEE create chart for the area of classified image

In Google Earth Engine I have classified a mosaic image using Random Forest, and using reducer the area of each class classified was determined by the code below. var area_classified = ee.Image....
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Convert SHAPE_AREA units via the REST FeatureServer API

All similar questions seem to involve desktop software but I'm strictly using the arcgis API like so: https://services2.arcgis.com/API_KEY_HERE/arcgis/rest/services/Category/FeatureServer/0/query?...
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Area given by software (QGIS and MapWindowGIS) DIFFERS from value given by revenue official [duplicate]

Revenue official has given area as 10.12 acres. I used QGIS and MapWindowGIS with projection UTM Zone 45 to measure area. The software gave area value of 13.06 acres. Why the difference?
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Calculating snow pixels in GEE?

I have to calculate the decline in snow in a mountain area of Peru (between two points = two mountains). This is the link to what I have. https://code.earthengine.google.com/?scriptPath=users%...
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Combining parcels that are adjacent and add up to more than 10 acres

I am using ArcMap 10.7. My task is to find a site to be developed for parking. Sites are supposed to be greater than 10 acres. But we can also look at adjacent sites that add up to 10 acres. I read ...
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1answer
27 views

How to sum the area depending from another field value in field calculator?

I have a landcover-layer with an attribute of the administrative region (GEN). I am looking for an expression in the field calculator to calculate the summarized area depending on the GEN-field value. ...
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37 views

Area commanded from given point

I want to define the area below a contour that slopes at a particular angle (say -0.05%) from a particular point, for many points. I have a DEM, and can compute contours at a particular level (say 200 ...
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50 views

Getting more accurate area size using QGIS

I'm using Natural Earth's shapefiles and try to match them to the real area size. I'm utilizing $area expression, but no matter what ellipsoid measurement I use the result seems to be very off. For ...
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2answers
74 views

PostGIS - Fast area computation on large overlapping (or not) polygon dataset

I'm co-developing an PostGIS based API that will work with complex and potentially large sets (>10k) of polygons, extracted from a large table following custom, user defined filters. I have ...
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1answer
35 views

Different styles of area in same shape layer

I'm using QGIS 3.16. I have the following problems: One of my shape-layer has several areas. Now I want to give every area a different style/colour. I already found the function to give all areas the ...
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Is it better to calculate area of a global raster using long/lat or using an equal area projection (e.g. Galls-Peters)?

I am trying to calculate the area of values in a global spanning raster with values of NA, 1, 2 or 3. I would like to know the total area of each category, however, the map is currently in lat long (...
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29 views

Editing areas in shapefile + scalebar

I´m using Qgis Version 3.16 I have the following problems: One of my layer has several areas. Now I want to give every area a different style. I already found the function to give all areas the same ...
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30 views

Area Difference - Attribute Table and Map

How can I setup plot areas to be identical in attribute table and map. In map and in attribute table I'm using the same " $area " designator. What's more interesting, the area of smaller ...
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28 views

Calculating area of from 10x10 degree tiff raster file using QGIS

I am new to QGIS. How do I calculate the area in 0.05x0.05 cells from a 10x10 tiff raster file? I guess I will have to do a loop function to get the areas from the 10x10 file but I have no idea how to ...
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30 views

Overlapping score for each feature in the merged layer after spatial joins

I've clicked on the Join attributes by location button and can join two layers. But in the merged layer, how do I find out percentage of overlap/intersect calculated for each feature? For example, in ...
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51 views

$area is not returning the correct value in QGIS

I'm working in a black QGIS project set to EPSG:27700 and a layer in EPSG:2770. When I measure the area of a polygon using the measure tool I get a value of 7594315ha. When I subsequently do this in ...
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1answer
103 views

Adding column with area values in attributes table with standalone PyQGIS

I would like to add an area column to the Attributes table using Python. I prefer not to use QGIS Python console. I would like to do that using cmd. How should I change my code? My code and error ...
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1answer
98 views

Working out percentage of polygon covering another using PostGIS [closed]

I have 2 polygon tables, polytable_a and polytable_b. a has 1000s of features and 100s of unique names (a1, a2, a3, a4.... etc) assigned to the polygons. b also has 250,000 features but only 3 unique ...
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1answer
83 views

Finding area of polygons within buffer [duplicate]

I have 102 different sites in two cities, which I have created buffer zones for. I also have layers that have polygons for different landscape features (e.g. water surface area). I am trying to find a ...
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1answer
43 views

Adding shapes to polygon feature in the same row

I've got somehow simple issue but cannot process it. I am working with shapefile in QGIS (3.10 on MacOS), where having several polygon features stored as rows. I want to somehow (manually) edit some ...
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1answer
52 views

Calculate percentage of each biome on each national state in QGIS

I have one shapefile of Brazilian states (black lines) and another shapefile of Brazilian biomes (colored areas). I want to add, on the states' attribute table, the percentage of each state's area ...
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55 views

How to calculate area of a double-line road network in QGIS?

I have a line vector file that displays a road network. Most roads consist of a double-line indicating the sides of the road (hence the width of individual segments), but some roads are indicated by a ...
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48 views

If I am using the coordinate system WGS84 ESPG:4326 and my cell size is 0.00833333,-0.00833333, how can I calculate the area of one cell in metres?

I am currently trying to undertake some area calculations on some rasters. I have them all in the coordinate system wgs84 ESPG:4326 which I have just realised is in degrees. My cell size is 0.00833333,...
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Calculate raster volumes within polygons - GDAL & Python [closed]

I have a shapefile with 625 polygons. I have a .tif raster DEM file at a 1m resolution. Objective: get 625 values that describe the volume of the raster (above 0m elevation) within each polygon. (...
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Why do I get missing data rows when I run this virtual layer area query?

I have a shapefile of circles called circlesdixie. I have a polygon layer called FCC (the shp download link at https://www.fcc.gov/reports-research/maps/auction-904-updated-jun20-eligible-areas/. I'm ...
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Changing the method of the area command from planimetric to ellipsoid in QGIS

I am trying to use the QGIS Field Calculator to calculate the area of a feature. When I do this, the area returned is calculated using the planimetric method. This differs to $area which uses the ...
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2answers
101 views

Intersecting area between two polygons in the same shapefile in QGIS

I have a shapefile with two polygons in it. I would like to be able to generate the intersecting area between the two polygons. Please note, I have tried using the intersect tool, however this does ...
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3answers
152 views

Calculating proportional area of polygon covered by circle [closed]

I have two layers here (ignore the green layer), blue polygons and black circles. I want to calculate for each circle, what percent of the each of the blue polygons does it cover. For example, the ...
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114 views

Masking clouds/shadows and calculating area using Google Earth Engine

I am using Landsat Surface Reflectance images to calculate the change in NDVI over time for an roi. I wanted to mask out anything that would give weird NDVI values so I used the code from Cloud mask ...
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33 views

Measuring tool and field calculator giving wrong area in QGIS 3.10.4

I've been consistently having issues with the QGIS measuring tool in 3.10.4. When I measure an area or line (regardless of the units) it gives a wrong value when compared to the measuring tool in ...
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1answer
173 views

Using advanced field calculator in QGIS Python console

I am trying to calculate area using field calculator in the Python console of QGIS. Here is the expression which I wrote. output8 = processing.runandload('qgis:advancedpythonfieldcalculator', "E:\...
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Using (area) instead of ({{bbox}}) does not include 2nd REL command

The following code does not include the result of (LINE 5). Why? area [name="Hawaii"][admin_level=4]; ( rel[type=boundary][place~"locality|city|town|village|borough|municipality&...
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1answer
80 views

Area Density Heat Map QGIS

I would like to make a heat map of "building density" based on the area of the building footprints (I have them in a geojson as polygons) in relation to their "non-building" ...
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1answer
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Does OSGB36 (EPSG:27700) preserve area?

What I mean is, if I have a map which uses the OSGB36 (or EPSG:27700) projection, and I draw two areas (let's say polygons) on my map which cover the same area on the map, does this mean that the real ...
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How to calculate the hill area in Google Earth

I want to calculate the area of this hill (the 3D area not flat area) located in Google Maps. https://www.google.com/maps/place/Oujda,+Morocco/@34.4788585,-2.0182252,434m/data=!3m1!1e3!4m5!3m4!...
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1answer
30 views

How to add virtual (e.g. $area) fields to multiple layers

I wondered if I could add virtual fields to the feature tables of a number of polygon layers in a QGIS 3 project (or a geopackage). As an example, I would like to add the virtual field area (km²) as ...
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34 views

Calculate total area of both adjacent and contiguous raster cells within a radial distance around a polygon's centroid

I have a raster containing grid-cell values of either 1 or no data, NA, representing used- or unused-habitat types, respectively. Using R's raster package, I want to calculate the total area (in ...
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66 views

Surface area of waterbodies for multiple location using Google Earth Engine

Using this code, I've extracted surface area of water bodies (for a period of 6 years) from sentinel 1 GRD dataset. But how can I compute water area extent of multiple location and produce chart/CSV ...
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2answers
105 views

Calculating green roof area in QGIS

I am trying to detect green roofs in a city and would like to compute the total area of green roofs (also on a per roof basis). I used a shapefile containing all roofs and used that to extract the ...

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