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Questions tagged [formula]

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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 ...
Soup Dragon's user avatar
0 votes
0 answers
51 views

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 ...
Noah P's user avatar
  • 59
0 votes
1 answer
66 views

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 ...
gis1234's user avatar
  • 319
1 vote
1 answer
569 views

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 ...
Bastien's user avatar
  • 639
2 votes
3 answers
267 views

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 ...
MartinMap's user avatar
  • 8,326
3 votes
1 answer
486 views

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" &...
Bruno B's user avatar
  • 849
2 votes
1 answer
119 views

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 ...
Mas's user avatar
  • 33
0 votes
1 answer
350 views

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 ...
Enrico's user avatar
  • 9
1 vote
1 answer
113 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 ...
Sajjad's user avatar
  • 61
2 votes
0 answers
232 views

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 ...
Ansharah's user avatar
1 vote
1 answer
184 views

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 ...
Siti's user avatar
  • 37
1 vote
1 answer
1k views

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 ...
ANSHARAH MOBEEN's user avatar
0 votes
0 answers
99 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 ...
Hardau's user avatar
  • 101
2 votes
1 answer
441 views

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....
Dolby's user avatar
  • 91
1 vote
1 answer
885 views

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 ...
ReutKeller's user avatar
  • 2,149
0 votes
2 answers
187 views

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 ...
Shapperd's user avatar
  • 101
1 vote
1 answer
188 views

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 ...
ee17hd's user avatar
  • 19
3 votes
1 answer
239 views

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 ...
lesto's user avatar
  • 317
3 votes
1 answer
113 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 ...
Bacon_Sammich's user avatar
1 vote
0 answers
44 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 ...
Sérgio Ferreira's user avatar
0 votes
2 answers
691 views

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: "...
Alp 's user avatar
  • 11
0 votes
1 answer
420 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
Bruna's user avatar
  • 1
7 votes
1 answer
581 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 ...
Laura Bennett's user avatar
5 votes
1 answer
976 views

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 ...
HanRF's user avatar
  • 95
4 votes
3 answers
2k views

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 ...
Nunkuat's user avatar
  • 495
1 vote
1 answer
430 views

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.?
Rob's user avatar
  • 173
2 votes
1 answer
126 views

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 ...
Taras's user avatar
  • 33k
3 votes
0 answers
500 views

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;...
BPDESILVA's user avatar
  • 161
2 votes
0 answers
2k 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 ...
Gaurav Borade's user avatar
3 votes
0 answers
568 views

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 @...
amizuka's user avatar
  • 31
0 votes
1 answer
1k views

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 ...
datakeen's user avatar
  • 473
2 votes
0 answers
2k views

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&...
Tom's user avatar
  • 121
0 votes
1 answer
2k views

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+...
Devdatta Tengshe's user avatar
4 votes
4 answers
11k views

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
Majed DH's user avatar
  • 183
10 votes
1 answer
26k views

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. ...
user66332's user avatar
  • 111