# Tagged Questions

The abstract study of topics encompassing quantity, structure, space, change, and other properties

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### How to calculate the intersection of 2 Circles?

I'm trying to figure out how to mathematically derive the common points of two intersecting circles on earth's surface given a center Lat/Lon and a radius for each point. Ex. Given: Lat/Lon (37....
4k views

### Calculating the distance between a point and a virtual line of two lat/lngs

Please refer to the example and corresponding image. I would like to achieve the following: provide two locations (lat/lng), which are shown below as A and B. From this, a virtual line would be drawn ...
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### Math and Stat for GIS and Computing

I am planning to do an advanced program in spatial science and engineering. It states as a requirement in the program, that the student should have a through understanding in math and statistics. So ...
2k views

### Calculating mean slope: Harmonic or Arithmetic Mean?

I have to calculate the average upslope percent slope for a large dataset, the basic method is detailed here. However, I've begun to wonder if harmonic mean might be more appropriate than the ...
3k views

### Determine angle down to horizon from different flight altitudes

I'm a pilot, not a GIS expert. What I need is a formula or a web site that I can supply the variables to answer my question. I need to know the angle down to the horizon from different flight ...
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### Understanding location storage and query algorithms?

One of the most important aspects of a GIS-equipped database is that it provides the user with the capability to quickly query for all points within some arbitrary geographic area that match some ...
960 views

### Find the nearest point on a line

I have a line that exists between two latlon positions, and a point on a certain latlon position. What I want to know is what the nearest point on that line is (in respect to the other point). So a ...
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### How to find a point half way between two other points?

I'm working on implementing the OSM Mobile Binary format for map data, and because it uses a 16 bit delta for each point along a way, it cannot represent a way if there is a large distance between two ...
12k views

### Calculate midpoint from a series of latitude and longitude coordinates

I've got a series of longitude and latitude coordinates which represent a building outline e.g. -0.5485381346101759,53.2285150736142 -0.5482220594232723,53.22842450827133 -0.5482298619861881,53....
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### Project location on a (great circle) path

I've been searching this SE site for quite a few hours now, and I'm still struggling to find a solution to my question. My goal is that given a way in OSM and my location (lat/lon coordinates), I want ...
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### RMSE between two rasters step-by-step

Can anyone show how to calculate the RMSE (root mean square error) between following two rasters step-by-step and discuss on the obtained results' min and max values, and how to interpret it. Thanks a ...
307 views

### Aerial photogrammetry book with all the math

Can anyone recommend a book that hits all the math for the general situation of doing serious photogrammetry calculations on aerial photographs? Particularly an inexpensive book or one I can get ...
1k views

### How to sum or even perform more complex mathematical operations (multiply, add a constant, …) two GDAL grids?

I have two grids with same cell size, same starting position (top left) and same grid size. I want to sum the grids and create a sum grid as an result: e.g. grid A + grid B = grid C How can I ...
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### Math module VS PostGIS

I have a simple (and maybe stupid) question for you today. I have to compute intersection points between GIS polygons and imaginary lines I draw thanks to a script of mine... And I wonder if it would ...
2k views

### How to “calculate” distance-to-ground of all 18 OSM zoom levels?

Assuming I'm building a 3D solution with the "world" being mapped to global geo-data supplied by OSM / Cloudmade... think http://www.webglearth.com but with completely different goals and use-cases. ...
2k views

### Drawing Ellipse with OpenLayers

I am trying to draw ellipse on the client side using openlayers with some mathematical functions from drawing ellipse with svg. I have achieved drawing it but not rotation what I have written for ...
3k views

### What formula is used for distance between 2 points in Google Maps?

What formula is used by Google Maps for calculating the shortest distance between 2 points (having their Lat, Lng coordinates)? Is it purely based on Haversine? Or is it something different? Is there ...
99 views

### Index express the similarity in shape between two data sets

I have two data sets. One is points in the blue curve. The other is points in the green curve. Now I want to find a property (P) or something else like index that has the following characteristics: ...
374 views

### Proper use of Modulus “%” operator in ArcMap [closed]

Objective: Gather pour points to define a specific-sized watershed. In this case, 1000 pixels. (for this thought exercise, watershed is to mean any point that flows through a pour point, regardless ...
379 views

### Finding Intersection of Two Circle given Lat/Lon and radius?

I am attempting to calculate the intersection of two circle on the Earth with a given latitude, longitude and radius. I started with this How to calculate the intersection of 2 Circles? These circles ...
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### Is it possible to solve Differential Equations in ArcMap and/or ERDAS Imagine?

I would like to know if it is possible to solve differential equations and run them directly in either ArcMap or ERDAS Imagine, similar to the raster calculator in ArcMap?
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### How to generate missing points in GPS trajectories?

I have some GPS trajectories that include gps locations recorded on variable frequencies (every 1 min ,5 min , 20 min,etc.)using a geographic projection WGS84. In my work, i need a fine-grained GPS ...
716 views

### How to place markers on the outline of a circle in google maps?

I have the center of a circle and it's radius and I need to place variable amount of markers on the outline/stroke of the circle. The distance between this markers should kept same, so if I have 8 ...
718 views

### How to convert latitude, longitude to EPSG 3857?

I'm looking to study the math involved to see how a given latitude and longitude in decimal degrees can be converted to epsg 3857. Can anybody point to a good reference or a possible python/c/c++/java ...
208 views

### T-shaped polygons

Is there any coefficient that can indicate T-shaped polygons ? Examples of T-shaped polygons :
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### Calculating angle of polyline at midpoint using Python/ArcPy?

Trying to calculate the angle of a line at its mid point using python; this will be used to display flow direction on a water network. I've developed this script, which works in terms of generating ...
100 views

### Convert Raster into Cell by Cell Table

I'm hoping to run some Python mathematics on a raster, outside of ArcGIS. It's important to have a cell by cell table for the analysis I want to run. I plan to store it in a python dictionary similar ...
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### Is there a method to tell which hemisphere a point belongs to, in WGS84 geoid, where the equator is an arbitrary ellipsis?

I use the WGS84 geoid (because I'm working with a GPS chip). I define an ellipsis that splits the surface in two parts, lets name these 'A' and 'B'. This ellipsis is defined by two points 'a' and 'b'...
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### What are the set of projections that can be accurately georeferenced using polynomial 2?

Background I'm starting with a map from the internet (Encyclopedia Britannica) and georeferencing it using QGIS 2.0.1, I get really accurate georeference solution using polynomial 2 transformation: ...
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### calculate turning acceleration from a compass

I have degree and timestamp and want to calculate the turning acceleration. What to trigger if the compass is turning fast. Is there a mathematic way to get an acceleration parameter?
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### Recreating A Lat/Long Grid Using a Specified Formula

I'm trying to recreate the Gridded Mercury emissions 2000 (0.5 x 0.5 degree grid) designed by the Arctic Monitoring and Assessment Programme. The file is in ASCII format, but without any coordinates. ...
353 views

### Comparing two maps with two different libraries

I'm currently making a demonstration to compare the two OpenLayers libraries (2 and 3). For doing this, I have made two div elements and put the different maps on each other. The goal is to make a map ...
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### How can i add script with math functions to model builder?

I am very new to model builder + python. (Sorry for my english too) I am trying to make a model. Don't know if it matters to upload it. If you want i can. I want to calculate variance from a points-...
388 views

### How do I calculate curvature using GIS co-ordinates [closed]

I have GIS data for which I would like to calculate where curvature is present. Anyone has done this before, please help.
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### How to resolve a rectangle with know points? [closed]

How do I find the coordinates(lat, lon) for D and E in the following rectangle? I know: A (lat, lon) B (lat, lon) C (lat, lon) AE, BE, AC
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### What mathematical processes does a GPS receiver use to determine position?

I'm writing a report on the mathematics of GPS, but I'm wondering what methods the GPS actually uses. What I've done is set up the four sphere equations and solve them using the Newton-Raphson method ...
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### Formula for charting a course around the globe, given a location and degree heading?

I'm looking for a formula that takes a long/lat coordinate and a degree heading, (e.g. "I'm standing in San Francisco and I'm facing 45º from north"), and which can draw a line across a map projecting ...
221 views

### How to locate a house on the 3D Map correctly?

I've done my 3D map generation in WebGL/THREE.JS project and have an issue with the building locations. I have the data about building position ( its polygon ) from DB server, but first of all I want ...
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### Bearing to X,Y, Z

I’m working on a small project where I’m testing the ability of a laser to accurately measure the angle of a wire. My control for the experiment gives me X,Y,Z coordinates for a point on the wire and ...
106 views

### mathematics of spatial diffusion models

There are different types of spatial diffusion such as contagious model, migration model, etc. What are the good books to learn about the mathematics behind these spatial diffusion models?
394 views

### How to take cosine squared of raster using python

I have an equation y = cos^2(x) where x is a raster. How can I write this equation in python?
409 views

### Do I need to run regression in each samples separately?

I'd like to do smooth NDVI image by regression analysis; response of time series NDVI image to Julian date to represent the seasonal changes in NDVI as a function of Julian day. The time series NDVI ...
285 views

### Find items within a Bounding Box

Not 100% sure if this is the correct place to ask my question so I apologise if it isn't. Also, I have very limited experience with GIS systems, so please pardon my ignorance if some of my terminology ...
61 views

### Calculate location on line with known azimuth to point

I have the following situation (consider distances up to 300m - without great circle etc. affects): How can I calculate the unknown location when I have all other locations in the triangle and ...
114 views

### Comparing compass bearings

I have several compass bearings: bTrue = 190° b1 = 250° b2 = 100° b3 = 170° b4 = 90° I want to compare b1 - b4 and find out how close they are to bTrue. So bTrue is 100%. How much percent is then ...
489 views

### How to determine vector between two lat/lon points

For all the math geniuses out there...given two lat/lon points (point A and point B), what is the simplest way to find the vector needed to reach point B from point A. For example, the vector needed ...
160 views

### math related sum distance problem (TSP content)

I hava an interesting problem related with GIS / MATH / TSP. If I calculate the distance between A and B on a x/y-style coordinate system it is obvious to use the following formula: sqrt((Ax-Bx)^2+(...
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### How do I compute uncertainties in the positions transformed using Helmert transformation?

I am familiar with Python, MATLAB and Mathematica. My data is given by Cartesian coordinates (positions in X,Y,Z (meters), standard deviations XX, YY, ZZ (meters) and a correlation matrix (XY, YZ, ZX)....