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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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25 views

Calculating area difference between two polygon shapefiles using QGIS

I have two polygon shapefiles which contain about 30 features. These features have different boundaries in both shapefiles so the areas are different too. I want to calculate that difference in the ...
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Doing change detection of land cover between 2 landsat images in google earth engine?

I am doing land use/ land cover classification of 2000 and 2018 year . I had completed supervised classification now i wanted to do change detection analysis. Please guide me how to do change ...
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Converting Google Maps Lat Long to Square meter area

I want to convert a set of 5 Lat Long (Directly taken from Google Maps) into Sq Meter area. As 5 points are there I have found the formula on Converting Longitude and Latitude Coordinates to Square ...
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27 views

How to smoothen and dissolve the output image and how to calculate the pixel areas of different classes in Google Earth Engine? [closed]

I am doing supervised classification of 5 different classes, I tried the code suggested in GEE tutorial but I can't able to understand the way they did. I am attaching my code here. Could someone ...
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32 views

Calculating the area of raster within polygon

I have a raster layer with values of energy demand in each cell. I would like to know the area of the raster within each polygon (see screenshot). Any suggestions on a simple approach for this?
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41 views

Calculating damage from a flood at the village level in percentage

I am using ArcGIS for my analysis. I want to calculate the damage from a flood at the village level in terms of percentage area damaged. I have done the following steps. My village file is in point ...
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1answer
34 views

Calculating the area of one layer inside area of another layer QGIS [duplicate]

I am currently looking at some Marine Protected Areas (MPAs) in Madagascar, and am trying to work out the percentage reef cover inside an MPA boundary. For example (in the picture below), I have the ...
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39 views

Area of one raster cell

I need to identify the area (m2) of each cell in a raster layer. I do know how to find the cell size under metadata (which in my case is [0.00980834,-0.00748333]); but how do I convert this into m2 or ...
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49 views

QGIS Identify feature Cartesian area in degrees

In QGIS 3, the identify feature tool automatically calculates area. However, there are two areas: Cartesian and ellipsoid. The first is being calculated in degrees (not wanted) and the second in ...
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12 views

Calculating fraction of area characterized with certain values?

I have a rasater data with cell values of the following: missing, 1, 2, 3, 4, and 5 Now I need to find the fraction defined as (area with value 5)/(Sum of areas with values 1,2,3,4) for a certain ...
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1answer
54 views

Surface area calculation in Google Earth Engine?

Using this code, I've extracted water extent in a Landsat median image. But how can I compute water area extent? code link: https://code.earthengine.google.com/8ad84d9ca59b3cb71b62f83119621bdc var ...
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35 views

Calculating area by classified image in Earth Engine

I want to calculate the area for each classified color in earth engine. Here are my codes. var image = ee.Image(ee.ImageCollection('LANDSAT/LC8_L1T_TOA') .filterBounds(roi) .filterDate('2015-01-...
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1answer
42 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
57 views

Getting the percentage area of intersecting polygons [closed]

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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24 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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17 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
71 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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42 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
49 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
46 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
37 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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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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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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42 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
80 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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76 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
76 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
29 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
43 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
65 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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39 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
56 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. ...
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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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76 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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1answer
162 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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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
157 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
136 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
230 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
650 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
34 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
237 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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38 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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35 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
32 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
33 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 ...
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1answer
120 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
185 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
299 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 ...