The first stage of sampling aims to generate sample sites, the sample sites on map of the region of interest provide their location and coordinates for the second stage of a field investigation. The number of sample units is determined by input parameters. The location of sample site is determined by the user to input the map of the region . According to operation flow chart shown, the first stage of sampling steps are as follows: |
|
Step 1: users enter basic information When you launch the software, first enter basic samples information, including the project file name and the save path, the location of the map of the region file, the generated sample site file name and its position; if user already has a sampling range, it can be loaded at this time. When users click on the confirmation, the software is responsible for creating the project files, loading the file of map of the region and displaying them. The generated sample site file and sample site file both with same with extension area are loaded to the software. |
| Step 2: Set sample regional information In this step, three things need to complete, selecting sampling model, setting up sampling resolution, selecting or drawing sample region. |
i.selecting sampling model: software is currently offering six sampling models to be chosen. Users according to their own information and expectations to achieve the purpose choose a different sampling model. According to user choice of model, the software will offer different input parameter interface. If choose a stratified random sample, spatial stratified random and the "sandwich" model, the software will require users to complete creating stratification files or import the files. The software provides three ways to get the stratification files: 1. Users directly load the files they already had. 2. Users draw stratification file on map of the region of interest, 3. Users input the classification files and obtain stratification file by classifying and stratifying method. If choose "sandwich" model, users also need to import reporting unit file. After obtaining stratification file, the software will deliver the stratification file to the graphic manager. The stratification file will be used as sample region. ii. Setting sampling target values type: Based on sample target users select scale or the proportion. According to different types of value settings, will enter different parameters and adjust different methods of calculating sample size. iii. Setting sample resolution: Through setting sample resolution user can obtain all possible sample unit capacity in survey area, which is the population size, equivalent to the size of the survey area divided by resolution. The software can real-time display a cell sample size at this resolution on the map of the region iv. Selecting or drawing sample region: If user chooses a simple random sampling, systematic sampling and spatial random sampling model, user have to select the sampling range or draw the sample range on the map of the region. The selected sampling range will appear in the software by clicking on different sample region (a sampling range comprises a number of sample region), Location of a sample region can be seen on the map of the region. If the other three models chosen, stratified region is sample region. |
| Step 3: Enter sampling parameters In the second step in accordance with user choice of sampling models, enter different sampling parameters and the different random sampling models and different target values will be changed along with it. Enter the input parameters according to the software instructions, the software will automatically choose calculation functions based on the user input. Input parameters may be a variety of combinations. (Users can reference parameter system) . |
| Step 4: Calculation of sample size and / or mean accuracy Based on the users selection of parameters, the software automatically selects all the possible combinations of the parameters and calculates various sample size and corresponding estimated mean accuracy in different parameter combination. The whole sample sizes from calculation are drawn on a graph with X-axis for sample size, Y-axis for accuracy. At the same time based on user input costs, the relationship between cost and sample size are draw on a graph called sample cost- size graph with X-axis for sample size and Y-axis for cost. Users, based on accuracy and cost requirements, will need to choose which function to be used (each algorithm deals with different sample sizes and estimated accuracy functions ) on the sample and then choose adjusted coefficient of sample size . During the sampling process, some samples can not be obtained or sample data may be lost. According to the user's choice of adjusted coefficient of sample size , the sample size will be calculated in accordance with a certain percentage increase, as the final sample size for users. |
| Step 5: Generating sample site In the sample space, sample process is carrying out based on the sample size and selected sample model. Sampling results will be saved to sample site file and displayed on the screen.At this site user can save the generated sample site map in other common graphics formats such as JPG and so on. When ending the process, the relevant parameters and file information used in the sample process can be saved to the project file. |