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Estimation and Simulation
Gridat provides main geostatistical Estimation methods like Ordinary
Kriging, Lognormal Kriging and Indicator Kriging. Estimation Variance
distribution models are available too.
Simulation methods, available
at
Gridat are Sequential Methods based on Ordinary, Lognormal and Indicator
data.
Setting initial parameters for
Estimation and Simulation are alike except for few parameters. Therefore how to
use
Gridat for both is referred here.
While your data sheet is
activated
[1], select
"Kriging Estimation" for estimating models or select "Sequential Simulation" for
simulating model from "Modeling" menu.
"Model Setting" window will be
appeared.
Select the data columns you
intended to use as X, Y, Z and W
[2].
There is some initial
statistical information about your data file here
[3].
You may intend to use data
collected from districted area.
Set your data limits here.
Default values cover all data, recorded to the active data sheet
[4].
You could reload default values
by clicking refresh signs.
If you want to remove suspected
data or highly suspected data from your process, check the appropriate checkbox
here
[5].
There is another tab labeled "Kriging"[6]. You can determine the initial settings for estimation or
simulation there.
Select "Kriging" tab and see
how you could determine initial parameters.
As you select "Kriging" tab,
Gridat start to calculate homogeneity for the area you allocated at
"Data" tab. Depended to your data file and your system capability, this may take
a few minutes.
"Don’t frighten.
Gridat has done most of setting for
you."
Gridat calculate the changes of varigram factors in the area through
directions and draw a "Rose diagram" according to its calculations. Then
recommend an ellipse (for 2D modeling) or an ellipsoid (for 3D modeling) for a
homogeneity model of the area. This model shows parameters "a", "C0" and "C" via
a 3D viewer object in the Homogeneity Ellipse/Ellipsoid area (Right side of the
window)
[7]. Look at the ellipse/ellipsoid carefully. If the ellipse or
ellipsoid does not obtain rose diagram (that is shown by gray lines)
[8] you could change parameters of ellipse/ellipsoid. As you see
parameters are diameters (a, b, c), Direction and Dip (for 3D models). Although
you will not need to be worried about homogeneity if you are not intended to use
homogeneity parameters as search area or Variogram parameters (as you know
Kriging method based on Variogram parameters and data points collected from a
specified search area).
Homogeneity models for
Variograms parameters would not be involved in calculating if you leave the
title "Obtain Homogeneity"[9] at "Variogram Options" tab unchecked. In this case
Gridat use a Variogram
with the parameters determined at the proper boxes
[10].
Gridat calculates these parameters too. But you could change them. You
could use parameters of an existing varigram model; you create it before, too.
Just select the name of your Variogram model from "Get This Variogram" list and
click on the title "Get This Variogram".
But if you check "Obtain
Homogeneity"[9] at "Variogram Options" tab, homogeneity models will be used as
Variogram parameters for Kriging calculations.
The search area Kriging collect
initial data from it would be determined at the tab titled "Search Options".
Gridat uses greater "a" value as search radius. You could change it or
you could order
Gridat to use an ellipse or ellipsoid that obtains homogeneity model.
Other search options related to your project specification and your
geostatistical knowledge.
There is another tab here under
the title of modeling area. You could determine the area you want to create the
estimated or simulated model for. Don’t mistake this area and the Data area
you’ve determined at "Data" tab
[4]. Try these options several times to understand how to use it.
Kriging method is selected by
Gridat [11] according
to your data normalization. But sometimes you may not agree with
Gridat. In addition if you need to use
indicator estimation or simulation methods, you must select "Indicator Kriging"
here. Then always be aware about this option.
Don’t forget as you change
Kriging method,
Gridat needs to create homogeneity again.
Refer to your geostatistical
knowledge for other options, especially when Indicator Kriging is selected,
because varigram settings are different there.
Now you are ready to view the
result.
There is just something
noticeable about 3D models. When you create 3D models there will be an extra
figure near the "Grid Size". It determines the number of sections you want to
create models at [12]. In other words when you set the figures equal to 50x50x3, you
order
Gridat to create three models with 50x50 estimated or simulated points
on it. These three models are alike at X; Y coordinates but different on
elevation. The elevation for each section calculated by
Gridat according to initial data Z
column value. But you could change them. Click "Levels"[13], double click the elevation you want to change, type your value
and press "Enter".
Sections value is shown under
the title of "Base Level" for 2D models. In this case the number of sections is
1 and the elevation is 0. You could shift up or down your modeling plate by
changing the value of "Base Level". It sometimes is very useful.
Now click on the Ok.
Gridat needs time for calculation. If it takes too long, press F12 to
cancel progress.
"Model Setting" window will be
closed.
Now "Models" tab is activated and your
model is created.
The title of the model is shown
at the left side of "Models" tab, indexed by a number
[14].
If you can't see it, select
"Project Explorer" from "View" menu.
You can't change the index but
the title of the map and other options could be edited.
There are several options for
models available on "Property bar", at the right side of Model
[15].
If you can't see it, select
"Model Property Bar" from "View" menu.
Try several changes to being
more familiar with this object.
For example you can indicate a
special value range by defining a different color at the color palette
[16].
All options are not available
for every model. For example "CurrentLevel" property is available just for 3D
estimated or simulated models. By changing this value you can view the model
created at each level [17]. To view all sections together you need to use "3D view" from
"Tools" menu.
If you want to change some
initial settings like data entry properties or Kriging parameters, right click
the model and select "Option and Settings" to access "Model Setting" window
again.
When you right click the model
a popup menu will be appeared and some commands would be available. These
commands are available at "Model Toolbar"[18] too. If you can't see "Model Toolbar", select "Model Toolbar"
from "View" menu. Try these commands to see how the model affected by each of
them.
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