Compiling points2grid on Fedora with g++

Gridding large [x,y,z] point cloud datasets. Matlab and python have both failed me with their inefficient use of memory. So I'm having to turn to other tools.

Points2Grid is a tool, written in C++, which promises to do the job in a simple intuitive way. It accepts ascii and las (lidar) formats and outputs gridded data, plus gridded data densities.

First install LIBLAS which is Lidar data translation libraries. The recommended version is 1.2.1. I installed liblas 1.6.1 because it was the oldest version on the site that had a working link. I installed this by issuing:

Make a note of where the libraries are installed. On my system: /usr/local/include/liblas/

Download points2grid from here. 

In Interpolation.h, adjust MEM_LIMIT variable in the  file to reflect the memory limitations of your system. From the README guide, 

"As a rule of thumb, set the MEM_LIMIT to be (available memory in bytes)/55. For jobs that generate

grids cells greater than the MEM_LIMIT, points2grid goes "out-of-core", resulting in significantly worse performance."

Find this value using:

I then had to point the code to where the liblas directories had been installed. In Interpolation.cpp, replace:

It should then install with a simple 'make' command. Happy gridding!

Compiling Clarkson's Hull on Fedora

A note on compiling Ken Clarkson's hull program for efficiently computing convex and concave hulls (alpha shapes) of point clouds, on newer Fedora

First, follow the fix described here which fixes the pasting errors given if using gcc compiler.

Then, go into hullmain.c and replace the line which says:



at the end of the function declarations (before the first while loop)

Finally, rewrite the makefile so it reads as below It differs significantly from the one provided.



Notice how the CFLAGS have been removed. Compile as root (sudo make)

Program for spatial correlogram of an image, in C

This program will read an image, convert it to greyscale, crop it to a square, and calculate it's spatial (1D) autocorrelation function (correlogram), printing it to screen.

It uses OpenCV image processing libraries - see here and here

Compilation instructions (in Ubuntu):

 sudo apt-get install libcv-dev libcv1 libcvaux-dev libcvaux1 libhighgui-dev libhighgui1  
 pkg-config --libs opencv; pkg-config --cflags opencv  
 PKG_CONFIG_PATH=/usr/lib/pkgconfig/:${PKG_CONFIG_PATH}  
 export PKG_CONFIG_PATH  
 gcc `pkg-config --cflags --libs opencv` -o Rspat Rspat.c  

Usage in the terminal:

 ./Rspat IMG_0208.JPG   

The program: