6
votes
Converting latitude, longitude (EPSG:4326) into EPSG:3857?
from pyproj import Proj, transform
P3857 = Proj(init='epsg:3857')
P4326 = Proj(init='epsg:4326')
x,y = transform(P4326, P3857, lon, lat)
- 329
5
votes
Accepted
Postgresql - problem updating row with complex calculation
The part being equal to zero is likely ((vitality + root_injuries + stem_injuries + crown_injuries)/16)) should the sum be less than 16. Try dividing by 16.0 instead so you will have decimal results.
- 39.8k
4
votes
Converting from ECEF to geodetic coordinates
You can use this function to perform the conversion of ECEF coordinates to Geodetic coordinates.
The function is implemented in python but can be easily written in java.
Example:
import math
def ...
- 1,343
4
votes
How to add meters to EPSG:4326 coordinates?
As explained by Mr. Che, general answer is to project in a metric system (for example, for Europe, you can use EPSG 3035).
However, if all your points are within a small area (~some dozens of km), an ...
- 91
4
votes
How can I calculate the coordinates of a point on the intersection of two parallel lines with a bisecting line with pyQGIS?
Combining grass:v.parallel and saga:convertlinestopolygons (both processing methods) in a PyQGIS code, it is possible to accomplish this task. For this situation:
and this code:
import processing
...
- 29.4k
4
votes
Accepted
ECEF coordinates to geodetic coordinates: Where is error in calculation?
About the ATAN2 function:
Your definitions for lambda (longitude) and psi (geocentric latitude) have a domain restriction:
lambda = ATAN(y/x) , with x > 0. (i.e., just for -PI/2 < lambda &...
- 13.5k
4
votes
Accepted
Calculate distance between location and way segment
In such cases the best strategy is to use existing solution/library, and in this case that would be turf.js library and it's method turf.nearestPointOnLine (see https://turfjs.org/docs/#...
- 22.8k
3
votes
Accepted
Translating latitude and longitude into "polar coordinates" around a point
Your cartesian to polar transformation would be valid after first projecting all your dataset in an azimuthal equidistant projection centered on your point of interest. You can find all details on ...
- 49.3k
3
votes
Bearing to X,Y, Z
Form (whole circle) bearing, zenith angle and horizontal distance to X, Y, Z
X = X0 + h_distance * sin(deg / 360 * pi())
Y = Y0 + h_distance * cos(deg / 360 * pi())
Z = Z0 + h_distance / tan(zenith / ...
- 7,112
3
votes
Accepted
How to generate missing points in GPS trajectories?
GPSBabel has a function for this. To take a GPX input file and interpolate points so that each is 30 seconds apart:
gpsbabel -i gpx -f INPUT.gpx -x interpolate,time=30 -o gpx -F OUTPUT.gpx
Arguments:...
- 14.8k
3
votes
Finding line equation (on Earth) using two GPS coordinates
If you think the Earth as a sphere, you probably looking for the great circle (orthodrome), the shortest path on the surface of the sphere. You should find the circle which is in the plain of the two ...
- 7,112
3
votes
How to determine left and right side of crossing lines?
Consider using the cross product approach as discussed here. Pure mathematical approach that does not rely on any third party module.
I would take the start point and test against the line. I think ...
- 42.6k
2
votes
Doing Math calculations within ArcMap Dynamic Text?
You can use the Data Driven Page Display Expression option . So in your case the display expression on the Display tab of the Layer properties would be SHAPE.AREA/10000
http://desktop.arcgis.com/en/...
- 115
2
votes
Math formula for transforming from EPSG:4326 to EPSG:3857
I got a C# code for using in unity engine.
Here the code below :
public static double[] latLonToMeters(double lat, double lon)
{
//Debug.Log(Mathd.Tan((90d + lat) * Mathd.PI / 720));
//Debug....
- 21
2
votes
Estimating resolution of vector data?
Great question - I’ve seen this type of question pop up numerous times and unfortunately, many people undertaking quantitative GIS analysis ignore the CRITICAL component of calculating uncertainty in ...
- 131
2
votes
Getting lat/lng of an object X inches from the GPS?
Someone can please correct me if I'm wrong, but:
The distance left/right in degrees of longitude depends on the latitude you are at. Calculating longitude length in miles? explains how that works. ...
- 13k
2
votes
How to add meters to EPSG:4326 coordinates?
You can't just add an constant value to geograghic coordinates in EPSG:4326: WGS 84 coordinate system, because the length of two arcs between two different pairs of point on a sphere is depend on ...
- 7,016
2
votes
Accepted
How to run a Epanechnikov (parabolic) decay in QGIS 3.6 field calculator
Your formula is correct and valid in QGIS, and will yield a Gaussian kernel:
However, the field you are trying to calculate needs more digits, since the exp decay you defined is very "slow" (the ...
- 6,364
2
votes
Accepted
Seeking documentation about non-iterative UTM to Lat-Long projection formulas
The part of the iterative method is not easy to understand.
I found the document on which you rely on the following link:
https://earth-info.nga.mil/GandG/publications/tm8358.2/TM8358_2.pdf
...
- 13.5k
2
votes
Accepted
High resolution x,y dataset for Mollweide projection convert to latitude and longitude coordinates
For the calculation of R, you will have to use half of your image width (144,000 / 2) = 72,000, which gives an R value of 25455.8441227.
Also, since the projection origin is at the center of the ...
- 3,786
2
votes
Accepted
Converting to geodetic latitude, longitude
Actually, the latitudes and longitudes that we commonly use are geodetic, not geocentric.
Unless specified that your latitudes are geocentric, they will most certainly be geodetic already.
A geodetic ...
- 3,786
2
votes
How to determine left and right side of crossing lines?
Here is an approach using Postgis, it shouldn't be difficult to replicate in Python, code finds the azimuths from the intersection to the starting points, if it geom A's azimuth is greater than geom B'...
- 3,444
2
votes
How to determine left and right side of crossing lines?
Here is working code example in Python based on great answer of Elio in Postgis.
from shapely.ops import LineString, Point
import math
def calc_azimuth(point1, point2):
"""Calculate ...
- 850
2
votes
Accepted
An application for measuring river length?
There is no single application that will do what you ask as you are underestimating the complexity of the problem. Medial Axis will indeed identify a centre line but then you need to prune the network/...
- 42.6k
2
votes
Calculate GPS elevation angle (Python)
If you convert the coordinates from lat/long to a datum that uses meters such as UTM, and also make sure your elevation values are in meters, then you just need to use the Pythagorean theorem to find ...
- 2,844
2
votes
Create a longer line segment from a shorter one?
You are using planar geometry equations (Euclidean distance measurement, etc.) on spherical coordinates, which will introduce errors.
If your data only cover a limited geographical extent, try ...
- 1,304
2
votes
Accepted
Create a longer line segment from a shorter one?
Proposal from @Jan Šimbera to convert coordinates to projected CRS EPSG:32737 (UTM zone 37S) and then use cartesian math would in this case work quite OK, since line length is only about 20km and ...
- 22.8k
2
votes
Accepted
Calculate the new x and y coordinate of the extent after rotating the map in MapViewer ArcGIS Online
Answer by @FelixIP:
Calculate center coordinate (x_cent, y_cent)
Subtract the center coordinate from current corner's (x - x_cent, y-y_cent)
Apply the formula above
Add the center coordinate back (x' ...
- 41
1
vote
Accepted
Procedure of transforming coordinates?
There are two atomic procedures here.
Convert the projected coordinates from the State Plane zone (in US survey feet) to latitude-longitude on NAD83. (specifically, Lambert conformal conic)
Convert ...
- 18.7k
1
vote
Calculate angle between nodes or point in line in QGIS
There is the angle_at_vertex(geometry,vertex) fonction in field calculator that
Returns the bisector angle (average angle) to the geometry for a
specified vertex on a linestring geometry. Angles ...
- 14.6k
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