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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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20 views

Customized Albers Equal Area Conic projections are cosmetic only or do they affect area calculations too?

I will be doing area calculations for 100+ countries using country polygons taken from GADM, a database of global administrative areas. I am using ArcGIS. The GADM data is in WGS84 and is unprojected. ...
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1answer
46 views

Getting the percentage area of intersecting polygons [on hold]

I have the polygons for census tracts within New York City. I also have the polygons for the parks. What I would like is % of the census tract area, with an added 400 meter buffer, that is park. I'm ...
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20 views

How to compare centrality of points in different shaped and sized polygons

Suppose I have several polygons of varying shape and size, each containing a single point. I want to compare the centrality of each point, and determine which point is more central to its polygon. I'm ...
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14 views

Using ST_Area(geography) with ogrinfo in command line?

I want to to calculate the ellipsoidal/spheroidal area of each grid cell of a vector grid using ogrinfo. When using ST_Area(geometry) I get the 2D planimetric area (which seems to be constant for a ...
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2answers
61 views

Turning degrees into square kilometres (km2)?

After running raster layer unique value report I have got pixel number and area in degree. How can I turn it in square kilometres (km2)?
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1answer
38 views

Comparing Tract-level data to State-level?

I'm using firearm trace data (available at the state-level) and attempting to compare it to socially disadvantaged areas (census tracts) by the way of regression analysis. Katz and Schnebly (2011) ...
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1answer
46 views

Search plot by total area of two adjacent plots

I've got some QGIS data where each plot is described with some attributes e.g. Shape_Area which is the field describing the area of plot in m2. Normally I search for plot using the expression e.g. ...
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1answer
40 views

ST_Area(geometry) with ogrinfo estimates a stable area per grid cell

I use ST_area(geometry) in order to calculate the area of each grid cell of a vector grid with LCC projection and 6x6km2 resolution. The CRS of the vector is: +proj=lcc +lat_1=45 +lat_2=22 +lat_0=38.7 ...
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1answer
26 views

Wrong/Different values from $area and Group Stats

As mentioned in other questions there seems to be a problem with $area when OTF is enabled. In QGIS3 it can not be disabled My project hast EPSG 31255, some layers area 31255 some have different crs....
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2answers
47 views

How to convert point data to different sized polygons representing Marine protected areas?

I am trying to map Marine protected areas. I have collected data of where all these areas are. The data is expressed as point data (seen within the top image). Within the attribute tabled I have a ...
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7 views

When tabulating area zone field doesn't populate in .dbf table

I am using the tabulate area tool to calculate area of habitat types around banding sites. Each site has a unique name, so I used that when selecting my zone_field in the tool. However, when I run ...
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0answers
41 views

Why are my polygon features area being calculated as zero?

I am trying to measure the area of polygons within a larger polygon. However some of them, seemingly without reason are being calculated as having zero area. The highlighted regions are calculated as ...
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1answer
56 views

Calculating area in the attribute field of a QGIS 3.4.3 project with multiple CRS

The area calculations in my project derived from the attribute field show values way below actual area, because the attribute field assumes the project CRS (EPSG:3857). However, this CRS should remain ...
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0answers
72 views

Intersection and area calculations in geographic vs. projected coordinates

I think one should do intersection calculations when layers are in the same coordinate system, and one should do area calculations in the appropriate projected coordinate system. The order matters, ...
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1answer
74 views

QGIS shows incorrect $area in label, but correct in field calculator

I tried showing $area of polygons in QGIS, and it always showed planimetric square degrees instead of metric units. No matter what I set in project general settings, the value remained the same. ...
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1answer
23 views

Extract a list areas and indices of multi-part polygons (SpatialPolygonsDataframe) R

I'd like to extract a list of polygons from a SpatialPolygonsDataFrame that include more than one area (so a polygon with a hole for example, or just 2 areas in one polygon entry in general). There ...
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1answer
41 views

How to calculate the area of several classes of a raster in a polygon of a vector file with QGIS?

I have some trouble with QGIS I have two layers of information: The first one a vector that contains 500 objects, with attributes such as number of population, and... A raster that has three classes:...
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1answer
59 views

Calculate area of ellipsoidal polygon with QGIS

There is online service of GeographicLib, by Karney, where one can calculate the area of ellipsoidal polygon without need of reprojection. Can one calculate the area of geometry in QGIS so as ...
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0answers
24 views

Accurate area calculation for countries worldwide individually [closed]

I have polygons of countries with its administrative divisions, I would calculate the areas of each division in a country accurately. I got the bounding boxes for each country, then I divided its ...
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1answer
54 views

Over calculation of area- How do I calculate correct acreage when there are stacked parcels?

I am currently interning for a county in the United States. I am working on the data and mapping needed to fulfill the Open Space Activity of CRS. Stacked parcels are causing me a massive headache. ...
2
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1answer
47 views

What the default unit in QGIS 2.18 $area is calculated and etc?

I'm a beginner in QGIS . We are using 2.18 version. What are the basic units for area and slope, etc? SI, so means m, m^2, °? Or I can set it by myself? If it's possible to set it, where?
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1answer
45 views

How do I compute the forest area for different regions?

I am currently struggling to compute the forest area of some regions. I am an absolute beginner with Google Earth Engine. I tried it 2 different ways, mostly by copying and editing code I found. ...
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107 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 ...
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0answers
27 views

How to get the area of the pixels of a raster in Africa Lambert Conformal Conic CRS in R

My question has been previously asked here (R How to multiply the values of the raster pixels with the true surfaces of these pixels?), I have to multiply the precipitation value of each cell by the ...
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1answer
107 views

Dissolve using attribute field and area

How can I dissolve a shapefile with polygons and keep the information of the polygons that have the bigger area in QGIS? example: two polygons with the same field values but one of them is bigger ...
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1answer
129 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 ...
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1answer
126 views

Calculating area under each polygon in QGIS [duplicate]

I would like to know how to calculate the area of the vector layer (red in the photo) under each polygon (white square in the photo). The red layer has the area (km2) in its attributes. But what I ...
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2answers
412 views

Calculating polygon area within polygons in QGIS?

I am new to QGIS - I want to estimate the area of the reef under a polygon grid. My shapefiles are already in meters, however I am having a hard time calculating the area under the grid layer. ...
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1answer
28 views

Area of classified pixels in an image collection

I am using Monthly History data of the Global Surface Water dataset (Asset id: JRC/GSW1_0/MonthlyHistory). I have filtered the images using .filterdate and .filterbounds for my region of interest (...
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2answers
133 views

Problem with the ST_Area in PostGIS [duplicate]

I have a question with a query in PostGIS. I try to calculate the area from a polygon. It actually works but the area-result is not correct. My Query is: SELECT name, ST_Area(way)/10000 AS hectares ...
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0answers
37 views

Calculating area for polygons in arctic areas

We are evaluating areas of ecological importance in the arctic. The asset areas are of different sizes (up to 10 square kilometres) from latitudes 64 to 80 degrees north. The areas also vary in ...
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1answer
22 views

Measuring areas of polygons in shapefile in the terrain [closed]

How can I measure the actual areas of polygons in a shapefile in the terrain. Some of the polygons in the file is in flat terrain and some in steeper places. Is there an easy way to do this?
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23 views

How to calculate area of 1 x 1 degree cells every one degree?

I've calculated mean data values of each 1 x 1 bin like this: import numpy as np from scipy import stats north=50.5 south=21.5 west=-110.5 east=-76.5 bin_lon = np.arange(west, east, 1) bin_lat = np....
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1answer
24 views

Raster Symbology Calculate Area Acres

Using ArcMap, I am trying to classify/consolidate the symbology of these agriculture classes into 3 categories: Hay, Pasture/Grass, and Cropland. I also need to find the sum of acres of each of these ...
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1answer
32 views

Calculating area of .shp polygon that intersects with feature of another shapefile

I am using ArcMap 10.6. I created a polygon (red). Some of it overlaps with a feature that delineates a city (green). The brown is where they overlap. In case it makes a difference that the shapefiles ...
4
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1answer
116 views

Selecting an amount of features that together sum up to a certain value?

I am looking for a way in QGIS to randomly select features within my shapefile. The selected features together need to sum up to more or less 2000m2. So, it is not selecting 10% of the features, but ...
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1answer
152 views

Understanding difference in polygon area calculated from ArcGIS Desktop and QGIS?

I'm calculating the area of ​​some polygons and realized that the values ​​are coming out differently when I do the calculations in ArcGIS and QGIS. The data is in Sirgas 2000 and projected for the ...
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1answer
260 views

Calculating Specific Catchment Area in QGIS?

I have tried to calculate the Specific Catchment Area in QGis from Specific Catchment Area and Flow Width Tool available through Saga. However, I got just SCA product with valour 0. I got a reasonable ...
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4answers
175 views

QGIS Geometry $area Field calculator function compared with Cadcorp SIS

I want to know what QGIS uses as a measurement when using the Geometry and $area function. As in is, the area calculated Sq meters? I am getting two different answers when using Cadcorp SIS and QGIS: ...
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1answer
37 views

Calculating area of raster for value range using ArcGIS Desktop?

I need to know the area occupied by values between 0.2 and 0.8 for my raster class : RasterLayer dimensions : 1813, 1883, 3413879 (nrow, ncol, ncell) resolution : 0.0002704818, 0.0002704818 ...
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1answer
75 views

Area difference between polygon layers

I would like to calculate the difference of area between two polygons. I tried using the Difference tool, but all it does is create lines that are different between my two polygons. I also tried the ...
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1answer
564 views

How to calculate the polygon area and create a column of results in R

I'm working with shapefile in R and I need to calculate the polygons' area that I created by Gdiference function, So ,now I need to create a column with the size of freshly polygons created, because ...
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0answers
16 views

vector from raster, with the information of the raster, for area estimation

As you will probably understand, i am new to using GIS applications and software. So far, i tried SNAP and now i am trying to learn just a few modules for certain research applications, in QGIS. I ...
3
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0answers
108 views

Difference in area calculation between QGIS and R

I used R to calculate the area of every land polygon of the world (Projection of the source shapefile: WGS84; CRS: EPGS: 4326). To do that, I loaded the required packages ("sp" and "raster") and I ...
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1answer
503 views

Calculate area with OpenLayers4 and Turf.js

I've been working with OL4 for a few months now but this is the first time I try to calculate an area and after some research looks like Turf.js seems like the way to go. First, allow me to add all ...
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1answer
62 views

Filtering out clusters of features based on collective area threshold using QGIS/python?

I have a map I generated that roughly estimates timber industry land ownership (designated by the green on the map) in the counties surrounding the Salish Sea in the US state of Washington: I want to ...
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1answer
65 views

Selecting a subset of a raster, based on aspect and slope, as input to calculate area

Background I created some digital elevation models and subsequently made a 2 layer raster for each containing the calculated aspect and slope using raster::terrain. Now I want to calculate the area of ...
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0answers
32 views

Calculate Feature Area in Shapefile, which crs to use?

For a global shapefile I would like to calculate the area per feature. If I understand correctly it is best practice to reproject your shapefile to a projected coordinate system. In the past I've used ...
2
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1answer
106 views

Postgresql - problem updating row with complex calculation

A calculation for the replacement value of a tree exists: Variables: index_price for species; circumference of tree; condition measures: vitality, root_injuries, stem_injuries, crown_injuries (A ...
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0answers
52 views

How exact is $area?

Background: I am doing some area statistics (how much of different properties is used for a specific type of use) based on ACAD-constructions. Both the from dxf converted shapes and the baselayer with ...