Questions tagged [formula]
The formula tag has no usage guidance.
35 questions
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Calculating Percentage in symbology
I'm trying to calculate a percentage of a filter against a total number and show in symbology so total number 583269 (Plots) formula is "Column A" > -123 (gives a result of 582962) I ...
- 11
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0
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63
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Formula to use in respect to spatial resolution, to calculate the appropriate amount of random samples for QA of raster data
I am trying to write a script that will automatically calculate the amount of random samples needed to compare my derived DEM data against my truth datasets.
The DEM data can vary in resolution from ...
- 59
0
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1
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91
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Introducing formula in Raster Calculator of ArcGIS Pro
What is the correct way to introduce this formula in the raster calculator?
It is the formula in order to calculate m-coefficient for L factor for RUSLE model.
O = slope in degrees
I tried multiple ...
- 319
1
vote
1
answer
930
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Mathematical formula to convert lat-lon to Lambert Conformal Conic
I want to manually convert coordinates (latitude-longitude in degree decimals) data into Lambert Conformal Conic (more precisely, EPSG:3347). I already know how to use GIS software functions for ...
- 649
2
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3
answers
354
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Setting a complex default value in QGIS 3.30 that does not update automatically
I'm currently using QGIS 3.30 and I'm trying to set a default value for a field based on multiple other fields, without having the default value update automatically whenever an attribute of the ...
- 8,396
3
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1
answer
636
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Filtering maximum and minimum length in QGIS Attribute table
My Dataset contains the field "length" with numbers from 1 to 100. I just want to filter data which are greater than 50 or which are less than 50.
I just use the formula:
"Length" &...
- 849
2
votes
1
answer
156
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Multiply and Divide functions do not have correct output in Google Earth Engine
I am trying to calculate standard deviation (observed - mean)/(mean)*100 but I noticed the part where you ".divide(longTermMean)", the math results results are incorrect. I tested out ...
- 33
1
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1
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521
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Modeler with raster calculator using QGIS
I'm trying to use the modeler in QGIS to calculate the NDVI on a raster image. The model is the one below:
In the "NDVI Calculator" algorithm I have set the parameters like this.
The ...
- 19
1
vote
1
answer
137
views
Calculating sigma in Google Earth Engine
I'm trying to calculate this formula in GEE:
∑ U(U-5)^2 (u is wind speed greater than 5)
when I use (.add) in my code it just give me a pixels that are greater than 5 in both of them at the same but ...
- 61
2
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0
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282
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MCARI index standard range and formula
What is MCARI's standard range of high and low value. Like NDVI range is from -1 to +1, so is it from -1 to +1 or different because when I am calculating it my range goes up to in thousands. Also if ...
- 21
1
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1
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209
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PyQGIS: Add threshold value based on user input in Raster Calculator
I want to use Raster Calculator in my Python script in QGIS. The expression is easy - I want to create a new raster with two values (0,1) where I get 1 if the pixel value is higher than a certain ...
- 37
1
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1
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1k
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Calculating vegetation indices NDRE AND RECI using Sentinel 2
I am trying to calculate NDRE and RECI using Sentinel imagery ON ArcGIS software . For RECI( RED EDGE CHLOROPHYLL INDEX) the formula is (NIR/RED-1).
Can you tell me which band to use in order to ...
0
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0
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102
views
Raster calculator expression
I'm looking for raster calculator expression which includes the "STATISTICS_MEAN" value from the raster properties.
How can I build the expression, that the value is automatically adapted?
I ...
- 101
2
votes
1
answer
499
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Calculate EBBI from Landsat 8 in Google Earth Engine
I am trying to calculate EBBI from Landsat 8 in Google Earth Engine (GEE) but I am getting this error: Error: Image.parseExpression: Expression parse error at character 30: '(SWIR - NIR)/ (10 * Image....
- 91
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1
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1k
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Using weight component in Moran I calculation
I'm trying to understand the Moran I calculation, and there is something I don't understand.
In this tutorial, Moran I described as the slope value of the correlation between one polygon to the ...
- 2,215
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2
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211
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Measure distance between two points
I want to code some converter in C# (I need it for a project), where I get two (or more) coordinate pairs from QGIS, in decimal degree pair format (47.xxxx,19.xxxx).
I need to measure the distance ...
- 101
1
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1
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233
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Strange values for index based built-up index (IBI)
I am trying to calculate index based built-up index (IBI) in ArcMap using raster calculator and getting strange values. I downloaded Landsat 8 data. To get the IBI, first I calculated NDVI with NIR ...
- 19
3
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1
answer
261
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Adding new row by command in field calculator in QGIS
I am actually trying to create a new field in a table with the Model Builder (Field calculator function).
Is there a command that creates a new field, so I can do calculations directly in that new ...
- 327
3
votes
1
answer
130
views
Changing 'NULL' value to '0' in label formula
I have a label formula in QGIS that shows the name of a polygon and the remaining km of survey left to do:
"Name" || '\n' || round("Length_km_sum", 2)
But when I have an area ...
- 379
1
vote
0
answers
45
views
Date format conversion brings an unexpected empty space between the date parts
I always used the formula (below) in Python Calculator to convert the date format from Julian to Gregorian format. But,now a weird behaviour is happening and I am trying to figure out what is wrong in ...
- 137
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2
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755
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Not working formula in Query Builder (Filter)
I have been trying to filter a big dataset based on multiple values. The idea is to extend the formula as put in the image below. But even the first part doesn't work.
When I do: "...
- 11
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1
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473
views
How to write it on ArcGIS Raster Calculator?
I just started using the Raster Calculator, so I don't know how to build the formulas.
How can I do this?
I need to write both of these formulas:
D = is a raster file called "Slope_2"
P = 13
- 1
7
votes
1
answer
742
views
Find out what Expression has been used to populate an attribute column in QGIS
I need to find out what expression has been used in the field calculator to populate a number of columns in the the attribute table in QGIS. Does anyone know how to get it to display this info? Like ...
- 203
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1
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1k
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Calculating polygon attribute based on intersection with grid in QGIS
I'm trying to use QGIS to profiling polygons in a layer. There is also another grid layer, each grid contains its own demographics information.
Assume the demographics are evenly distributed within ...
- 95
4
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3
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2k
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Calculating attribute with formula in QGIS
I want to build a QGIS formula where I calculate one attribute from 10 others, and I only need to sum them up.
My Problem is, that I don't get the actual values of the attributes. I thought about ...
- 507
1
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1
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531
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What are the formulas used in SAGA Ordinary Kriging?
can some one name the formulas avaible in the Ordinary Kriging Modul of SAGA:
What ist the exponential, spherical, Gaussian-Model, etc.?
- 173
2
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1
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134
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Flow data distribution within features of overlapping layers
I want to improve/adjust/comprehend the formula (see below) that was used in my previous question: Transferring flows (connections + values) between polygons for calculating flow values of mobile data ...
- 33.9k
3
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0
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533
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Conversion to_string provides NULL in QGIS
I've been trying to convert a decimal row into a string row using a few methods. Below is my CSV file:
also, note that csv header has been updated too,
State;AverageRainfall;ProbabilityBelow;...
- 161
2
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0
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2k
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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 ...
3
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0
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592
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QGIS: processing-modeler to add multiple layer name to attribute field
I'm trying to add layer name using the field-calculator in QGIS (3.4.1). If I do this manualy it works fine, but if I do this using the processing-modeler I get NULL for every field. I just type @...
- 31
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1
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1k
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Formulation of CRS (EPSG2438 to EPSG4326) conversion in Excel
I have about 14000 points with coordinates EPSG2438 and want to convert the coordinates into WGS84 (EPSG4326). I want to know that is there a way to make Excel formula to convert these coordinates. In ...
- 473
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2k
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Finding center of circle given three points?
I have been trying to solve this problem for quite some time, but can't find a good solution.
Given three sets of geographic coordinates how can I calculate the center point. By "center point&...
- 121
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What is the Formula to get an Image's Bounding Box from it's GDAL GeoTransform Array?
I have a process which needs to read in an Image's GeoTransform Array, and convert it to the Bounding Box
i.e. If the Input is:
<GeoTransform>
7.8087700868360430e+05, 9.9974951285737870e+...
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5
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4
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11k
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Math formula for transforming from EPSG:4326 to EPSG:3857
Is there any math formula for transforming from EPSG:4326 to EPSG:3857 ?
i want to implement it in php code
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1
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27k
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Calculating View Angle
I am looking for the most accurate way of calculating the view angle (Azimuth, Elevation) from a reference point (my location) A to another point B. I have the Lat, Lon, and Altitude for each point.
...
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