- Double-click
SSSampling. pop-up under interface
Figure 1. starting interface
- Under sample plan: Click on
,
Choose a suitable file path to save the project files, such as: “sampling project” - Under map of the region of interest : Click on
, choose the hs_town.shp file - Under the sample site layer: Click ,
choose a suitable path and enter the name of the file with sample site information, for example: sampling site
2 - 4 steps, as shown below
Figure 2.
Input the correlative project file
- Click on the "Finish"
- Note: If at this time a sample range file and the map of the region of interest are area based object, there will be no need to change of the sampling region settings. If the map of the region of interest is site based object, the sampling range should include object region for the sample site (for example, the sample site is samlingframe.shp, the sample region is hs_county.shp)
- After the previous step completed, click out of the following interface
Figure 3.
The setting graph of the sampling area
- Choose "Simple random sampling model"
- Set sampling resolution as 0.01, move pop-up window, you can see in the middle of map of the region of interest there is a small box, this is the smallest sampling unit based on input sample resolution. According to input different sample resolution, the size of the box will change in real time (if the map of the region of interest is site based object, there's no need to set up sampling resolution)
- Select sampling region: There are three options (each method will need to be tested, but only one may be used at a time)
i. Employing this region: Select the polygons underlying the map of the region
ii. Manual option: hold down the shift key while clicking to select a polygon, you can select multiple polygons, and then click on the “End” button on the Toolbar
iii. Expert draw: Use the mouse to draw the sample polygon region, left-click start drawing, right-click to complete, and then click on “End” button on the Toolbar. - Click on the "Scale" (or ratio, determined according to sample target value)
- Click on the "Next "
- After the previous step has been completed, click out of the following interface.
Figure 4.
Compute the sample size
- Input parameters and verify the correctness of the input parameters
- Click on the "Compute Sample Size," and obtain the graph of relationship between precision and sample size and cost
- Select a different function; obtain a different sample precision relationship graph
- Click on the name of calculation functions, we can see that each function uses different parameters
- Select "Proportion", which is the actual number of samples compared to the theoretical value, as shown below
Figure 5.
The graph of calculating sample size
(The left is accuracy-sample size graph, the right is cost-sample size graph, the input cost can be displayed on the right)
- Click on “Back” to return the parameters interface, can modify parameters
- Click on the "Finish", determined sample function
- Back to the design parameter interface, click "Finish", complete sample size calculation and system will generate sample site.
- Double-click SSSampling，
launch pop-up interface:
-
Select "Open Sampling Design " to open the project file which
generated in the first step.
- Click OK, click out of the pop-up dialog for sample data input
- Select input file, open the saved data file (the file format is txt), then select the property of the calculation value (generally value)
- Or select manually input file, enter value directly under the value field in the form. Then select the property of calculation value.
- Sampling model has two kinds of situations
i. Directly click "Next", obtain sampling results
ii. Select sampling model, and then select spatial random model, get different results. Or choose stratified, spatial stratified and sandwich sample model, this time pop-up dialog box, which need to enter the relevant stratification file(for example: If the data is in order, natural stratification file using stritify.shp, reporting unit using hs_town.shp, which only used in the sandwich model).
Figure 7.Input the data
- Click on the "Next", show up a sampling results map
