Questions tagged [area]
Area is a quantity that expresses the extent of a two-dimensional surface or shape, or planar lamina, in the plane.
523
questions
2
votes
1answer
61 views
Getting area of shapefile polygons in square kilometers using R?
Firstly, my shapefile has an undefined projection:
library(raster)
x <- shapefile('file.shp')
Warning message:
In .local(x, ...) : .prj file is missing
crs(x)
CRS arguments: NA
I know that my ...
2
votes
0answers
27 views
Calculate real surface area with PostGIS
I would like to know if its possible to calculate a real surface area (with DEM information) only with PostGis function ?
I know it's possible with Saga and Grass.
0
votes
1answer
21 views
EPSG codes for projections to use when computing the area of global polygon sets in python env
The general answer to this question is "Use any equal area projection in units of meters that covers the world". Python code needed to make use of this is short and sweet:
import geopandas as gpd
...
1
vote
1answer
29 views
Why does polygon area change when projection is changed in ArcGIS Desktop? [closed]
I have a simple polygon in a given coordinate system (example see below) as a feature in a FGDB. I would like to re-project the polygon to ETRS 1989 LAEA (EPSG 3035) using the project tool (data ...
0
votes
0answers
33 views
Area measurements in Google Earth
Since Google Earth works in degrees, how does it perform area measurements? Does it momentarily convert to Cartesian coordinates and if yes by what projection and on which datum? Web Mercator has the ...
0
votes
1answer
74 views
Calculating water body area in Google earth engine using Landsat images?
I am attempting to calculate the area of water bodies in my classified map using landsat images in Google earth engine. from youtube I found a tutorial on GEE which showed me a method of calculating ...
1
vote
0answers
22 views
Getting less calculated area after merging/dissolving polygons [closed]
After I merge/dissolve polygons together, the area I calculated using the field calculator seems to decrease, in comparison to the calculation of each individual area and then summing it up.
Can ...
0
votes
2answers
50 views
Forest change tutorial results don't make sense compared to area of the country
I've been following this Earth Engine tutorial on calculating forest loss by country, and running that same code for multiple other countries. What I had matched the expected output that the tutorial ...
2
votes
2answers
54 views
Summing Area of polygons within vector layer within zone using QGIS?
I have one vector layer with multiple polygons (purple). I also have a number of other vector layers which are catchment zones (I also have a layer where these catchments are merged).
Is there any ...
2
votes
0answers
18 views
Raster:area() in R before and after projecting data
I have the following snippet of code:
tracts<-readOGR('data/.')
proj4string(tracts)
"+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +...
1
vote
1answer
22 views
Image analysis about area
I tried to find out the lake's area in an image raster - I used NDVI and reclassify then I got a whole value file like this.
Is there anyone can tell me how to divide them to each polygon?
Or I can ...
1
vote
1answer
34 views
Getting area covered by intersection or junction?
I need a way to get following information for each intersection or junction in Berlin:
latitude and longitude
area covered
I could get all Junctions from openstreetmap as nodes, which would give me ...
0
votes
1answer
27 views
Area size of polygons with same value (building id) in GRASS GIS
Is there a way to calculate the area size of multiple polygons having the same value (in this case building number) like group stats in QGIS?
0
votes
1answer
24 views
Making Time Series of different Class areas in ImageCollection
Here I can only calculate the area of the four classes(classes:0,1,2,3) of the surface water for one year. Is there any way to calculate areas of the four classes from 2000 to 2015 and export it as ...
0
votes
1answer
21 views
Calculate the area of a map using gdalinfo
I'm using gdalinfo to get some information out of a map, and want to use it to calculate the area represented by the map. I'm currently doing it (when the units are given in metres), by multiplying ...
1
vote
1answer
113 views
Calculating the Area by Square Feet with Geopandas
I have a geodataframe that has no assigned crs. I want to create a column/field called 'area' that has the area calculated as square feet, not meters or km, using geopandas. Note: this geodataframe ...
0
votes
1answer
28 views
Correct area calculations: When to use planimetric, when ellipsoidal?
Sometimes I am not sure whether to use planimetric or ellipsoidal model to calculate areas of polygons. If there is a "reference" data (e.g. a given shape_area column) I compare results and take the ...
1
vote
1answer
32 views
Split polygons by area/percentage with QGIS 3.x
Is there a function in QGIS 3.6 Noosa that allows me to split polygons with given area or percentage? There is a plugin for QGIS 2. "split polygons" that seems to have exactly what I'm looking for, ...
1
vote
1answer
22 views
Finding area covered by unmasked pixels in an image in Earth Engine
I want to calculate the area covered by forests in a region. Using Hansen image I have demarcated the forest regions in India. Now, how do I get the total area of forests?
// FILTERING OUT FOREST ...
1
vote
1answer
46 views
Calculate area, length, width of rectangles in shapefile with Python
I have a list of rectangles imported from a shapefile into Python in degrees. (EPSG:4326)
rectangles = [{'type': 'Polygon',
'coordinates': [[(-61.55002968237319, 73.546895599812856),
(-61....
1
vote
1answer
61 views
Choosing correct zoom level to display given area in square km using Leaflet?
I would like to set the zoom on a Leaflet map based on an area (in km^2).
I am looking for a simple function that would approximately convert an area of
510,064,472 km to zoom level 0 and (if I read ...
1
vote
3answers
69 views
Calculating areas of world map in QGIS?
I have a dataset with polygons of administrative areas for the whole world (https://www.gadm.org/download_world.html).
I want to have the area size of each polygon in square kilometers.
I saved the ...
0
votes
1answer
69 views
QGIS - processing area and calculating volume of polygon with know elevation from a DEM
I got a DEM of a watershed and I need to create a dam at a fixed elevation (with a rectangular polygon corresponding at the top of the dam) and calculate it's area (including the slope (fixed value) ...
2
votes
1answer
45 views
Determining the area in Sq Miles of 1 polygon that are contained completely within another polygon
I am looking to determine how much of the area of 1 polygon (Lets say a body of water for instance) falls completely with in another polygon (Call it a state or county for instance) i have a layer ...
0
votes
1answer
55 views
Where can I find the legend?
I have downloaded the following two tiff files from here:
pnv_biome.type_biome00k_c_1km_s0..0cm_2000..2017_v0.1
pnv_biome.type_biome00k_sse_1km_s0..0cm_2000..2017_v0.1
Using r.report in QGIS 3.6 I ...
1
vote
0answers
57 views
How to create a function for getting a largest polygon from 2 polygons using case statement in PostgreSQL?
CREATE OR REPLACE FUNCTION public.largest_polygon1(
geom1 geometry,
geom2 geometry)
RETURNS geometry
LANGUAGE 'plpgsql'
COST 100
VOLATILE
AS $BODY$
begin
Return
Case
...
-1
votes
1answer
134 views
Adding Area column in Polygon layer using PyQGIS? [closed]
I have a WardBoundary.shp file with Polygon Features in it. I have to calculate the area of each Polygon and write into attribute Table.
I can do manually by using '$area` but I need to automate ...
0
votes
0answers
16 views
Raster of land area within 15 km radius
I have two polygon layers, one of Land and one of Reef. I would like to create two rasters, of the Reef layer, who's values are the area of Land within 15 km of each cell, and the area of Reef within ...
1
vote
2answers
32 views
Calculating areas in continuous raster of flood map?
I generated a flood hazard map (raster) of a certain area using ArcGIS 10.5 and classify the result into
low 0.1 ÷ 0.5
medium 0.5 ÷ 1.5
high > 1.5
After that, I overlay a Land Use map (...
1
vote
1answer
76 views
What causes difference between two sources?
I have downloaded ESA global land cover tiff file and opened it with QGIS 3.6. To measure Africa separetly I used polygon file of this continent as a mask. I got the result that total area of Africa ...
0
votes
1answer
73 views
Measuring area using correct CRS and units in QGIS
I have uploaded a shapefile and I am simply trying to calculate some simple areas of provinces (and I know their areas from Wikipedia). My map is from Zimbabwe, and I have saved the project, ...
0
votes
0answers
23 views
Doing large calculations using Export in Google Earth Engine?
I need to calculate builtup and nonbuiltup area for the complete country on India.
The following code gives a "computation timed out error".
var geom = India.geometry();
var area_classifyed = ee....
3
votes
1answer
64 views
Same equal area projection results in different areas when shifting the center of projection
I found that using an equal area projection results in different areas for the same polygons if you shift the center of projection (ie to minimize the distortion of your area of interest when you ...
1
vote
1answer
35 views
QGIS 3.4 $area not equal for same shape
First, I created a regular grid of the size 1km^2 (epsg: 2056). Then I calculated the area of of this grid using different GIS:
Python: arcpy
area_arc
# Python Setup
import arcpy
arcpy.env....
0
votes
1answer
22 views
Select By Attribute - Get Parameter as Text - User input SQL ArcPy
I am trying to create a script that will search for suitable site locations.
I want to let the user input an area size (e.g. >20) to be searched but each time I run the script it comes up as
Error ...
0
votes
1answer
43 views
Understanding difference between area calculation when using zonal statistics tool and identify button?
I am working in ArcGIS Desktop 10.5 and I am a beginner.
I have very basic, non-overlapping polygons over a raster that represents bathymetry data. I need to figure out various statistics about each ...
2
votes
1answer
68 views
Knowing/converting AREA, PERIMETER units in QGIS?
I use Convexhull tool in QGIS and there are result value :
AREA = 0.0017494390 PERIMETER = 0.1725495172
I thought the result was strange. So, I took a rough estimate of the points through the ...
1
vote
1answer
49 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 ...
0
votes
0answers
375 views
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 ...
1
vote
0answers
232 views
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 ...
1
vote
1answer
67 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 ...
1
vote
0answers
66 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?
1
vote
0answers
42 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 ...
0
votes
1answer
43 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 ...
0
votes
0answers
43 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 ...
1
vote
1answer
166 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 ...
0
votes
1answer
17 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 ...
1
vote
1answer
420 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 ...
2
votes
2answers
437 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-...
1
vote
1answer
97 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. ...
