Questions tagged [formula]

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8 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 ...
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2answers
35 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 ...
2
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0answers
14 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 ...
3
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1answer
63 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 ...
3
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1answer
51 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 ...
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0answers
50 views

Image normalization in ENVI

I want to normalize dem images that min= -49 and max=229 to -1 and +1 in ENVI. what is that formula in band math?
1
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0answers
33 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 ...
-1
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2answers
183 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: "...
0
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1answer
110 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
6
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1answer
106 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 ...
4
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1answer
506 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 ...
4
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3answers
848 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 ...
0
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1answer
177 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.?
2
votes
1answer
108 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 ...
2
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0answers
219 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;...
1
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0answers
821 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 ...
2
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0answers
266 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 @...
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1answer
612 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 ...
2
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0answers
875 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" I mean ...
0
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1answer
975 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+...
4
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4answers
7k 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