BMEGUI Tutorial 1 Spatial kriging

Transcription

1 BMEGUI Tutorial 1 Spatial kriging 1. Objective The primary objective of this exercise is to get used to the basic operations of BMEGUI using a purely spatial dataset. The analysis will consist in an exploratory analysis of the data across space, in the modeling of its spatial covariance, and in obtaining a map showing the distribution across space of BME estimates of the data. 2. Install BMEGUI Go the website for BMEGUI version 3.0.1, and follow the instructions on installing BMEGUI on your computer 3. Data Download the data file data01.csv from the Tutorial Data Files and save it in a folder called work01. Open the data file using a spreadsheet editor (such as Excel, etc.) or a text editor (such as Notepad, WordPad, Word, etc.) to see the fields (i.e. columns) available in this data file. Note that since BMEGUI requires all data files to have a time field, data01.csv has a time field containing the same dummy time value of Operation i. Launch the BMEGUI by double clicking on BMEGUI desktop icon(see the BMEGUI user s manual for more details) ii. Select the following workspace and data file. Workspace: work01 Data File: data01.csv Note: Do not check the check box 'Use River Network'

2 Figure 1: Data file and directory selection BMEGUI screen iii. iv. Click on the OK button. The Data Field screen appears. In Data Field Setting section, select the following column names from the dropdown menu of each field. X Field: X Y Field: Y Time Field: T ID: Automatic ID Data Field: Z v. In the Unit/Name section, input the following units and name of data in each entry box. Space Unit: deg. Time Unit: days Data Unit: ug/l Name of Data: Contaminant A

3 Figure 2: The Data Field screen vi. Click on the Next button. The Data Distribution screen appears. vii. viii. Check the basic statistics (mean, standard deviation, coefficient of skewness, and coefficient of kurtosis) of the data and its log-transformed data in the Statistics section. Check the histograms of the raw data and log-transformed data. By clicking the Raw Data and Log Data tab in the Histogram section, you can switch the histograms.

4 Figure 3: The Data Distribution screen showing the Histogram of Raw Data (left) and Log Data (right)

5 ix. Click on the Next button. The Exploratory Data Analysis screen appears. x. Click on the Spatial Distribution tab and examine the spatial distribution of the data. Figure 4: The Spatial Distribution tab in the Exploratory Data Analysis screen xi. Click on the Next button. The Mean Trend Analysis screen appears.

6 Figure5: Mean Trend Analysis screen xii. xiii. xiv. xv. Since we skip the mean trend analysis in this exercise, click on the Next button. The Space/Time Covariance Analysis screen appears. Click on the Edit Spatial Lags button in the Experimental Covariance section. A dialog box appears. Input the following values in Spatial Lag and Spatial Lag Tolerance field in that dialog box. Spatial Lag: 0.0,0.01,0.02,0.03,0.04,0.05 Spatial Lag Tolerance: 0.0,0.005,0.005,0.005,0.005,0.005 Click on the OK button. The experimental covariance plot (shown in red dots) is automatically updated.

7 Figure 1: The Space/Time Covariance Analysis screen and the dialog box for modifying the lag size xvi. xvii. In the Covariance Model section, input 1 in the Number of Covariance Structure field. The tab labeled Covariance Structure 2 disappears. In the Covariance Structure 1 tab, input the following model parameters. Sill: Input the value of Variance (1.2073) Spatial Model: exponentialc

8 Spatial Range: 0.03 Temporal Model: exponentialc Temporal Range: 1 xviii. Click on the Plot Model button. The plot of the covariance model is superimposed on the experimental covariance plot. Figure 2: Updated experimental covariance and covariance model xix. xx. Click on the Next button. The BME Estimation screen appears. To obtain the maps of the BME mean estimates at a time of 1.0 (day), set the following estimation parameters in the New Map section. BME Parameters: Use the default settings Estimation Grid: Estimation Time: 1.0 Check the toggle to turn on the Include Data Points Display Grid: Use default settings Other parameters: Use default settings

9 xxi. Click on the Estimate button. Two new tabs labeled Plot ID: 0001(Mean) and Plot ID: 0001(Error) appear and a new entry appears on the list in the Maps Estimated section. Figure 3: The BME Estimation screen xxii. xxiii. Click on the Plot ID: 0001(Mean) tab and examine the map of the BME mean estimates. Click on the Plot ID: 0001(Error) tab and examine the map of BME error variance.

10 Figure 4: The maps of the BME mean estimates (left) and the BME error variance (right) xxiv. Click on the Quit button to close the screen. A dialog box appears. Click on the OK button of that dialog box to confirm that you want to quit BMEGUI.