# Questions tagged [formula]

The tag has no usage guidance.

35 questions
Filter by
Sorted by
Tagged with
31 views

### 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 ...
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 ...
• 59
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 ...
• 319
1 vote
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 ...
• 639
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 ...
• 8,326
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" &...
• 849
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 ...
• 33
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 ...
1 vote
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 ...
• 61
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 ...
• 21
1 vote
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 ...
• 37
1 vote
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 ...
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 ...
• 101
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....
• 91
1 vote
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 ...
• 2,149
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 ...
• 101
1 vote
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 ...
• 19
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 ...
• 317
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 ...
1 vote
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 ...
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: "...
• 11
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
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 ...
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 ...
• 95
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 ...
• 495
1 vote
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.?
• 173
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 ...
• 33k
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;...
• 161
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 ...
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 @...
• 31
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 ...
• 473
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&...
• 121
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+...
• 41.4k
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
• 183