as topic, the Coordinates value (Latitude and Longitude) is known , these Coordinates will compose as polygonal area , my question is how to calculate the area of the polygonal that is base the geography ?
thanks for your help .
First you would need to know whether the curvature of the surface would be significant. If it is a relatively small then you can get a good approximation by projecting the coordinates onto a plane.
Determine units of measure per degree of latitude (eg. meters per degree)
Determine units of meature per degree of longitude at a given latitude (the conversion factor varies as you go North or South)
Convert latitude and longitude pairs to (x,y) pairs in the plane
Use an algorithm to compute area of a polygon. See StackOverflow 451425 or Paul Bourke
If you are calculating a large area then spherical techniques must be used.
If I understand your question correctly - triangulation should help you. Basically you break the polygonal to triangles in such a way that they don't overlap and sum their areas.
Related
How to calculate Altitude from GPS Latitude and Longitude values.What is the exact mathematical equation to solve this problem.
It is possible for a given lat,lon to determine the height of the ground (above sea level, or above Referenz Elipsoid).
But since the earth surface, mountains, etc, do not follow a mathematic formula,
there are Laser scans, performed by Satelites, that measured such a height for e.g every 30 meters.
So there exist files where you can lookup such a height.
This is called a Digital Elevation Modell, or short (DEM)
Read more here: https://en.wikipedia.org/wiki/Digital_elevation_model
Such files are huge, very few application use that approach.
Many just take the altidude value as delivered by the GPS receiver.
You can find some charts with altitude data, like Maptech's. Each pixel has a corresponding lat, long, alt/depth information.
As #AlexWien said these files are huge and most of them must be bought.
If you are interest of using these files I can help you with a C++ code to read them.
You can calculate the geocentric radius, i.e., the radius of the reference Ellipsoid which is used as basis for the GPS altitude. It can be calculated from the the GPS latitude with this formula:
Read more about this at Wikipedia.
I am currently creating a feature and patterning it across a flat plane to get the maximum number of features to fit on the plane. I do this frequently enough to warrant building some sort of marcro for this if possible. The issue that I run into is I still have to manually set the spacing between the parts. I want to be able to create a feature and have it determine "best" fit spacing given an area while avoiding overlaps. I have had very little luck finding any resources describing this. Any information or links to potentially helpful resources on this would be much appreciated!
Thank you.
Before, you start the linear pattern bit:
Select the face2 of that feature2, get the outer most loop2 of edges. You can test for that using loop2.IsOuter.
Now:
if the loop has one edge: that means it's a circle and the spacing must superior to the circle's radius
if the loop has more that one edge, that you need to calculate all the distances between the vertices and assume that the largest distance is the safest spacing.
NOTA: If one of the edges is a spline, then you need a different strategy:
You would need to convert the face into a sketch and finds the coordinates of that spline to calculate the highest distances.
Example: The distance between the edges is lower than the distance between summit of the splines. If the linear pattern has the a vertical direction, then spacing has to be superior to the distance between the summit.
When I say distance, I mean the distance projected on the linear pattern direction.
Currently I'm trying the following: I have points from google earth (WGS84) which I want to transform to a local x,y coordinate system: a tangential plane with y positive from south to north and x positive from west to east.
There is no need for the plane to be part of a global coordinate system more than the relation (x=0, y=0) = (lat,lon). The scale at which I'm working is in the order of say 100 kilometers (maximum of for example 200 km's). Very small errors (due to for example the curvature of the earth) are acceptable.
I have relatively little understanding of this topic as of yet. Can anybody help me out? Where would I need to look for example.
Thanks!
I haven't found the answer mathematically but have found that the package basemap (of the mpl_toolkit) should help with this respect (from wgs84 to a transverse mercator projection).
Actually I have the decimal values of latitude and longitude.
In a 2d referential, are those values the x an y coordenates?
example :
in a position P
latitude = 41.15 longitude = -8.64
So, in a 2d dimension P is defined by (41.15,-8.64) ?
Thanks
No, its exactly opposite:
The coordinate (lat, lon) corresponds to the pair (y,x)
So when passinge lat, lon to mathematical routines, like point in polygon calculations
pass in order (lon, lat).
longitude raises parallell to the aequator, which corresponds to our x achsis direction we normally use in cartesian (x,y) systems.
Unfortunatley for historical reasons, the latitude is often written before longitude. (The cause might be that the latitude was easier to determine than the longitude.)
This all leads for us SW developpers to the bad situation, that sometimes functions use (lat,lon) order, sometimes when working with transformations from (lon,lat) to (x,y) or mathematical routines, the order lon, lat must be used. Be careful, every person I know someday has accidentally exchanged that.
In your example:
P is related to (-8.64), 41.15).
But lat,lon are spherical coordinates, for most application you must convert them to cartesian (x,y) .
But this is another question.
Be careful with units. In systems like Google Maps, those numbers are usually in degrees. Usually.
They might also be in radians, though, so at least make sure of what unit the API is using.
Greetings,
I have two coordinates:
(52.4412396, -6.563223)
and
(52.8912397, -6.683669)
The delta is:
(-0.4499999, 0.120446)
The distance moved is:
sqrt((-0.4499999)^2+(0.120446)^2)
=.465840261
How do I convert this to meters?!
I hope someone can help.
Many thanks in advance,
You have mistakenly done the sum of squares on spherical coordinates. Each difference has to be converted to its longitudinal and latitudinal distance before getting the hypotenuse. While latitude converts directly to distance, (each degree is equal to 60 nautical miles) the longitude will only do that at the equator) That means that you have to multiply the above by the cosine of the latitude. Then you can move on to a simple hypotenuse calculation before converting to meters.