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

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18
votes
3answers
2k views

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 ...
12
votes
3answers
2k 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 ...
11
votes
4answers
542 views

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 ...
9
votes
3answers
1k 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 ...
8
votes
3answers
168 views

Location storage and query algorithms. How do they work?

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 ...
7
votes
3answers
3k views

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 ...
7
votes
2answers
1k 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 ...
7
votes
1answer
664 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 ...
6
votes
1answer
2k views

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 ...
6
votes
1answer
110 views

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 ...
6
votes
1answer
104 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 ...
4
votes
3answers
188 views

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 ...
4
votes
5answers
7k 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 ...
4
votes
2answers
1k 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. ...
4
votes
1answer
1k 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 ...
4
votes
1answer
826 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 ...
4
votes
2answers
1k 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 ...
4
votes
0answers
313 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 ...
3
votes
1answer
203 views

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?
3
votes
1answer
412 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 ...
3
votes
1answer
117 views

T-shaped polygons

Is there any coefficient that can indicate T-shaped polygons ? Examples of T-shaped polygons :
3
votes
1answer
648 views

How to calculate angle of polyline at its 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 ...
3
votes
1answer
54 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 ...
3
votes
1answer
51 views

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 ...
3
votes
1answer
145 views

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: ...
2
votes
1answer
449 views

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. ...
2
votes
1answer
123 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 ...
2
votes
1answer
59 views

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 ...
2
votes
1answer
361 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.
2
votes
2answers
47 views

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 ...
2
votes
0answers
129 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 ...
1
vote
3answers
854 views

How to do Math within ArcMap Dynamic Text?

Is it posssible to perform any math on ESRI ArcMap dynamic text? For example I have the area of a SDE park layer's SHAPE.AREA, but it is in m2 because the layer is in NAD_1983_UTM_Zone_17N. I want ...
1
vote
1answer
90 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?
1
vote
2answers
90 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?
1
vote
1answer
213 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 ...
1
vote
1answer
210 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 ...
1
vote
1answer
45 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 ...
1
vote
1answer
175 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 ...
1
vote
1answer
122 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: ...
1
vote
0answers
35 views

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, ...
1
vote
0answers
14 views

How to organize/cluster nodes moving on the same direction

The Problem I am working on a problem of clustering for mobile nodes. Initially, I though of clustering the nodes based on their angle of movement (relative to the x-axis). However this situation ...
1
vote
1answer
67 views

Finding the shortest distance between a point and a line

I read and understood the following GIS question and the accepted answer, calculating-the-distance-between-a-point-and-a-virtual-line-of-two-lat-lngs I can return the value in the ShortestLength ...
1
vote
0answers
481 views

Trilateration Math Check

I'm trying to crate an indoor trilateration program working off of N BLE objects. Where I have any number of beacons in a room and my ipad can track its location within them to a sub meter degree of ...
1
vote
0answers
342 views

Trilateration issue

My program isn't making use of any geographical data, but I'm hoping that the users experience in the subject can help me with my current issue. The project I am working is trying to locate a user in ...
1
vote
0answers
14 views

strange misplaced markers on the map [duplicate]

Possible Duplicate: place markers on the outline of a circle in google maps I used word Strange because I'm not expert in this area, and it really looks weird to me. I've already asked a ...
0
votes
3answers
432 views

Calculate 'Rectangle' Coordinates Given 2 Points and width [closed]

I want to create a rectangular polygon using two points as guides. So let's say a journey starts in Egypt and ends in London, my polygon should have 4 points: 10 miles further from London than Egypt ...
0
votes
2answers
802 views

Detecting invalid polygons (self-intersecting or touching)

An invalid polygon can be defined as one that intersects itself, or one where the lines make contact, ie, the two shapes at the top of this picture. Given the XYPoints of a polygon, what logic ...
0
votes
1answer
80 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 ...
0
votes
1answer
95 views

Getting GPS coordinates perpendicular and parallel to AB

I already posted this question here And I got the solution thanks to Fang but the problem is that the coordinates I need to use are GPS coordinates and apparently GPS needs a different formula than ...
0
votes
0answers
27 views

how do calculate nearest point in earth map with coords

I am having trouble calculating nearest point for another point with earth coordinates. I am particularly interested in calculating the intersection of linestring vector with earth coordinates. I'm ...