Questions tagged [area]
Area is a quantity that expresses the extent of a two-dimensional surface or shape, or planar lamina, in the plane.
532
questions
3
votes
1answer
44 views
How to display the current polygon area when editing in QGIS 3?
I use QGIS 3.10 to create new polygons manually.
I want to see the area of an object interactively during its creation.
I know that after creating a polygon, you can automatically calculate its ...
1
vote
1answer
43 views
Unexpected results for area calculation on two datasets in Google Earth Engine
I'm seeing a very strange result using .pixelArea() on two different layers that should yield identical results.
Code within GEE is here, also reproduced below:
var states = ee.FeatureCollection("ft:...
2
votes
1answer
79 views
Error in area calculation
When I run the field calculator to update area, the resulting areas are too large. This happens whether I use QGIS 2.18 or QGIS 3.4.
The default CRS is set to: ESPG:27700, OSGB 1936 / British ...
0
votes
1answer
60 views
ArcGIS projected area greater than geodesic area
Question
Shouldn't the geodesic area always be greater than the planar area of a polygon?
Background
Tested in ArcMap and ArcGIS Pro, but several my polygons in a shapefile are having projected ...
-1
votes
1answer
40 views
Calculating area with ArcGIS ModelBuilder
This seems deceptively complicated. I have a clip of a large multi-polygon featureclass, and several of the polygons transect the clip barrier. How do I calculate the area of the new bisected polygons ...
0
votes
2answers
33 views
How you get the square containing a multipolyline
I use ST_Union to group a few lines. But realize some lines aren't supposed to be joined together after all. I would like to calculate the extent of the multipolyline so if the area is too big ...
0
votes
0answers
47 views
Completing network edges through an area using osmnx
Context
I want to plot a network (i.e. a graph, topologically connected where routing algorithms can be used) from openstreetmap data (this is linked with the python code snippet presented here: ...
1
vote
0answers
28 views
Elevation distribution of protected areas using QGIS
I am using QGIS.
Based on a DEM and a vector layer of polygons for protected areas in the Alps, I would like to calculate the areas of the respective protected area polygons in certain altitude ...
1
vote
1answer
57 views
Defining polygon's area from OpenStreetMap
In OpenStreetMap, I have a multipolygon OSM feature with its relation ID 6040040 (example).
How do I calculate the area of a such features using QGIS?
1
vote
0answers
56 views
Decimal places in SQLite
I'm working with a locally stored SQLite database and have an area field that auto populates via a virtual field using $area. Works fine but there seems to be no way to set the precision in a decimal ...
2
votes
1answer
94 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 ...
3
votes
0answers
42 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
28 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
59 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
36 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
177 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
54 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
64 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
19 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
25 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
41 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
33 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
25 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
28 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
309 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
61 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
54 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
34 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
76 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
77 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
98 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
147 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
64 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
69 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
203 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
18 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
80 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 ...
1
vote
1answer
100 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
28 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
71 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
38 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
42 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
78 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
84 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
60 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 ...
1
vote
0answers
520 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
318 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 ...
