User Guide for DigEMAn (Digital Elevation Model Uncertainty Analysis)

** Theory **
Program for uncertainty analysis & multi windows size
Multi windows based on Jo Wood's thesis Chapter 4
	http://www.soi.city.ac.uk/~jwo/phd/
LHS: Latin Hypercube Sampling
	McKay, M.D., Beckman, R.J. & Conover, W.J. 1979. 
	A comparison of three methods for selecting values of input variables in the analysis of output from a computer code. 
	Technometrics, 21, 239-245.
	Iman, R.L. & Conover, W.J. 1982. 
	A distribution-free approach to inducing rank correlation among input variables. 
	Communications in Statistics Part B-Simulation and Computation, 11, 311-334.


The program works as follows:

-Input DEM (with its uncertainty/ std_dev)
-Determine windows size, 3x3 or 5x5 or 7x7 etc...
	nside=1, 3x3 windows cells will look like, centre no.5:
			7 8 9
			4 5 6
			1 2 3

	nside=2, 5x5 windows will look like, centre no. 13:
			21 22 23 24 25
			16 17 18 19 20
			11 12 13 14 15
			 6  7  8  9 10
			 1  2  3  4  5

- For each point in DEM:

* Extract the neighbourhood
* calculate its local variogram
* Fit a model through the semivariogram data (gamma)
* LHS elevation of the windows cells : elev_1, elev_2....elev_ns1
	For elev=1 to ns1
		* Fit a quadratic response surface, use 1/gamma as weight
			get the parameters, a,b,c,d,e,f & their std. dev
		* LHS parameters a,b,c,d,e,f : par_1, par_2, ... , par_ns2
		  For par=1 to ns2
			calculate terrain attributes
		  next par
	next elev
* average the terrain attributes & calc the std dev

The uncertainty of the terrain attributes is the sum of the uncertainty in elevation & uncertainty in the DTM model

Max. 4000 rows & 4000 columns of dem

** How to use it **
Modify the dem.ini file with your parameter values
the description on left hand side of the '=' sign should not be modified

infile='dem_test.txt'
Input data file, ascii text file with x,y,z,(std_z)
name should be enclosed by quotation mark '  '

output file name
outfile='demout.txt'

dis=10
distance/resolution of dem cell

nside=2
number of half windows size for terrain attributes calculation
nside=1 will give 3x3 neighbourhood, 2 will give 5x5, etc...
use 2 for this instance

ntype=4
type of variogram, 
(1) sperical, (2) exponential, (3) gaussian, (4) stable model, (5) Matern, (6) generalised gauchy
reccomended for dem: (4) or (5) avoid using (3) and (6)
if ntype=0
no variogram modelling, the weight is unity
ntype=-1, weight is inverse proportional to distance from the centre point
ntype=-2, weight is inverse proportional to squared distance from the centre point


ns1=20
number of LHS for uncertainty in elevation, 
for DEM without uncertainty set ns=1, data file will only have 3 columns: x, y, z
if ns>1 data file should have 4 columns: x,y,z,std_z

ns2=20
number of LHS for uncertainty in quadratic modelling, for terrain attributes calculation

iprint=0
iprint=1 will print all the realisations of elevation & calculated attributes, and parameters of the variogram, large file..

iplot=1
attributes to be displayed 
1,2, 3, 4.. correspond to the order of the output attributes, e.g. 1= slope, 2= aspect.. see 'output' below
if iplot=0: no graphic display

pmin=0
min value for the graphics scale of attributes defined above

pmax=10
max value

islop=0
islop=0 use elevation for semivariance calculation,
islop=1 slope is used for semivariance,
islop=2 use std dev of elevation for semivariance calculation.

** Output

The output files will give x, y, z, attributes:

>From Wilson & Gallant
slope	: in %, perform arctan(slope/100) to convert into degree
aspect	: in degree
profc	: profile curvature (in 100/m2)
planc	: plan curvature
gradc	: gradient/tangential curvature
>From Shary:
meanc	: mean curvature
unsph	: unsphericity
diffc	: differential curvature
minc	: minimum curvature
maxc	: maximum curvature
>From Jo Wood:
longc	: longitudinal curvature
crosc	: cross sectional curvature

The std dev of the attributes will be given in the same name as output file with 'sd_' prefix
The realisations of the attributes will be given in the same name as output file with 'sim_' prefix
The parameters of variogram will be given in the name with 'vario_' prefix

** Running batch
Execute:
Digeman.exe dem.ini