Site sampling fixed point
Field sampling is fixed by GPS instrument combined with topographic map or survey network. Survey network is generally used in large-scale stage, and the layout of survey network should be carried out in accordance with Specification for Geophysical and Geochemical Exploration Sites (ZBD/0002).
The fixed-point error varies with the working scale. 1:25000 and 1:50000 soil survey shall be conducted according to the requirements of regional geochemical exploration specifications and geochemical survey specifications, 1:25000,1:50000.
The coordinates displayed by GPS instruments used in the field should be corrected by the regional correction coefficient, or by the coordinates of three triangular points in the survey area and its periphery, and the error between the corrected GPS coordinates and the actual coordinates of topographic maps is less than 5 m; At the same time, select obvious landmark points in the survey area, check and correct all GPS system deviations, so that the corrected GPS coordinate error is less than 5 m.
When sampling, not only the GPS coordinates of sampling points are recorded, but also the coordinate information of each sampling point is entered into the track column of GPS instrument to form a daily track map. Track information should be downloaded from the computer on the same day or every other day and printed on A4 paper for safekeeping, and a special person should be appointed to download the track information. See table 3-4 for the fixed point and trajectory management of GPS instruments.
Table 3-4 GPS coordinate correction record
When sampling, due to the limitation of terrain or traffic conditions or other reasons, it is impossible to reach the design sampling point, or the design sampling point cannot collect qualified samples, or the design sampling point is unreasonable, and the actual sampling point exceeds the fixed-point error. The sampling point change registration should be made on the specially-made sampling point change registration form, and signed by the project leader for confirmation.
2.2 Basic requirements for field positioning. GPS instrument
(1) general rules
The field sampling of geochemical survey is fixed by the combination of topographic map preparation and hand-held GPS instrument. The sampling points should be correctly marked on the hand map of1∶ 50,000 topographic map.
(2) Initialization of handheld GPS instrument
Before the formal field work, it is necessary to initialize the GPS instrument, detect the fixed-point error and calibrate it with the coordinates of the known triangular coordinates in the survey area. The calibration error is less than < 15m. The fixed-point error of GPS instrument in survey area is less than 50m.
When the GPS instrument is initialized, the coordinate format of the handheld GPS instrument should be selected according to the specific conditions of the work area. The coordinate system selection of hand-held GPS instrument should be consistent with the topographic map of the survey area. Generally, Beijing 54 coordinate system or Xi 'an 80 coordinate system is selected according to the topographic map used. If Gaussian coordinates are used, the central meridian of Zone 6 in the work area should be entered before work. According to the specification requirements of different types of GPS instruments, input relevant parameters in user-defined coordinates, including the central longitude value, projection ratio, east-west deviation, north-south deviation, and DX, DY, DZ and DF values of local coordinate belts. For Beijing 54 coordinate, DA = "- 108 ",DF =" 0.0000005 For Xi 'an 80 coordinate, DA = "-3 ",DF =" 0 three parameters DX, DY and DZ vary from region to region.
(3) Error correction of hand-held GPS instruments
More than three national triangle control points should be selected for error calibration and parameter correction of GPS instruments. 1. After all the different types of working GPS's δ X, δ Y and δ Z are zeroed, put them on the national third-level control points for accurate reading. The requirement must be a three-dimensional fixed point, and the number of fixed-point satellites should be more than 4. Record the GPS coordinate values of each point (Table 3-4), compare them with the theoretical values on the topographic map, find out the parameter values of δX, δY and δZ of GPS at each point, and then calculate the average values of δX, δY and δZ of GPS, and take these values as the GPS parameter correction values of the whole region to carry out unified GPS parameter correction.
(4) Field work scheme of hand-held GPS instrument
1) for field sampling, hand-held GPS instruments and spare batteries should be carried. Before field work, check the battery capacity of hand-held GPS instrument, and replace it in time when the battery capacity is insufficient.
2) track reservation. The route and trajectory of GPS instruments must be maintained during work. It is required that the hand-held GPS instrument used should have sufficient capacity. Pay attention to adjust the interval of automatically generating trajectory points, and generally choose 3 ~ 5 minutes to automatically generate a trajectory point.
3) fixed point. When working in the field, reach each sampling point, and take readings after the signals received by GPS instruments are stable. In addition to automatically inputting the trajectory, you should also input the coordinates of this point and record it in the record accordingly. Due to the terrain and vegetation, the GPS instrument must not be turned off during the restricted operation, so that the hand-held GPS instrument can keep the track automatically input at any time.
(5) Computer inputs sampling points and flight trajectories.
Every day after work, the sampling point information (coordinates, sample number, date and GMT) stored in the GPS instrument will be transmitted to the computer for storage (Table 3-5), and the data will be exported in two formats, namely. Txt and. Gdb format. After the entry is completed, the quality of the entry should be checked immediately.
(6)GPS data management
1) Trajectory data and trajectory map shall be managed by special personnel, and no one may call or modify the trajectory data without permission. The original data of downloaded tracks are recorded on the CD-ROM in the unit of 1∶50000 map.
2) Carry out quality management according to topographic map and track map. The two should be basically the same, and each input sampling point should be superimposed with the trajectory map to form a trajectory monitoring map. Every sampling point on the map should be distributed on the trajectory line.
3. How to use the handheld GPS instrument-Take Trimble as an example?
Trimble is a compact device that integrates GPS, digital camera and PDA. The device integrates GPS, PDA, Bluetooth, WiFi, digital camera and other functions, and adopts Microsoft's latest Windows Mobile 6. 1 operating system, including simplified Chinese in more than ten languages.
(1) fine switch
Start: Press and hold the power button for 4 seconds (in full shutdown mode) (see Figure 3- 14), and Trimble will start and stop the machine.
Shutdown: Press and hold the power supply for 5 seconds to completely shut down the system.
On-hook mode: press the power button to release immediately (in this mode, the system is not turned off, but the power consumption is the same, which is only suitable for equipment not to be used for a short time. Please don't turn off your phone if you don't use it for a long time.
(2) coordinate system
Select the coordinate system and correct three parameters.
Table 3-5 Structure Table of GPS Positioning Data
Description of data item:
1. Sampling point number. This number has been compiled before work and can be read directly or obtained through the acquisition system. For the filling method, please refer to the description of sample number in Appendix A of Regional Geochemical Exploration Code.
2. Sample bag number. Fill in the sample bag number.
3, 4. Positioning date and positioning time. Fill in the date and time automatically recorded by GPS.
5, 6. Longitude and latitude. These two items are obtained directly through the GPS positioning system. For the separated GPS, workers read the coordinate values and fill in the form; For integrated GPS instruments, automatic filling can be obtained directly through the acquisition system; Latitude and longitude can be filled in decimal degrees or degrees, minutes and seconds (for example, 1 12 45' 35.5 ",filled in as1124535.5"); One filling format must be unified in the same form.
7, 8. abscissa and ordinate. Gauss-Kruger projection is used for plane coordinates, and 6 bands are used for scales less than or equal to 1∶50000, and 3 bands are used for scales greater than 1∶50000. The plane coordinates are accurate to the meter, with 7 digits in the ordinate (north direction) and 8 digits in the abscissa (east direction), of which the first two digits are code names. Automatic conversion of coordinates obtained by GPS instrument.
9. altitude. Record the elevation of the sampling point in meters.
Figure 3- 14 Trimble Profile Description
(3) Workspace
1) opens the project.
① Open the project file. Click File → Open Project to open the workspace list, select the name of the workspace to open, and open the workspace (Figure 3- 15).
Figure 3- 15 Open the project file
Only one workspace file can be opened at a time. To open another workspace, you must first close the current project.
When selecting a workspace, you will be prompted to open the file, select the file to open, and click the "Open" button. The data file in this workspace will be opened and you can edit the data. Only one data editing file can be opened at a time. If you want to edit other data files, just open them directly, and the previous data files will be closed.
② Open the data file. Click File → Open File to open the data file list interface, select the data file to open, and click Open to edit the data file in this workspace (Figure 3- 16).
Figure 3- 16 Open data file
③ On-site editing. Select the data file to edit, click the "Field" button to open the editing function of the data file attribute field, select the element to edit, and delete and add the attribute.
Attribute addition: Click the "Add" button to open the attribute editing dialog box and directly define the attribute. Please refer to the editing function of data dictionary in RealMap Office desktop software for specific definition rules.
Attribute Delete: select the attribute field to delete and click Edit → Delete to delete it.
④ Add data files. Click the "Add" button to open the data files in all folders, select the data to be added and add it to the current workspace.
⑤ Close the data file. Click Close to close the selected data file, which will be deleted from the current workspace.
2) Close the project
Click File → Close Project to close the current workspace.
3) New projects
① Create a new project file. Click File → New Project (Figure 3- 17) to open the new project dialog box, enter the project name "Ancient Tree Survey", and click Create to complete the creation of the workspace.
Figure 3- 17 New Project and Creation
Figure 3- 18 Introduction of Acquisition Point Interface
② Create a new data file. Click File → New File to open the New File dialog box, enter a file name, and then click Create to complete the creation of the workspace data file.
(4) Data acquisition and input
1) Introduction of acquisition point interface.
See Figure 3- 18 for the introduction of the acquisition point interface.
2) point coordinate data acquisition
By selecting point elements in hand-held GPS instruments, small-sized objects such as street lamps can be measured and the coordinate position information of the target can be obtained.
After selecting the corresponding elements, enter the data acquisition interface. "e, n, h" is the coordinate value of the current position, which should be in a state of small range jumping due to the error of GPS.
First, set the Collection Interval. It is recommended to set the acquisition interval of one point to 5 seconds. Click the icon to collect data. After "Record Status", a red value will step by "1", indicating that the GPS instrument is collecting data every set time. Click the icon at any time, and GPS will average all the data collected before, complete the collection of coordinate data at this point, and fill in the attribute field information at the same time.
Note: The more times the points are collected, the more accurate the positioning will be. It is recommended that the take-up time should not be shorter than 30 seconds.
3) point coordinate data input
When the coordinate data of the target point is known and the input point is used for manual drawing, click Drawing → Input Point in turn (Figure 3- 19).
Enter the known coordinate data, write the attribute information, and then click OK to complete the point element entry.
Figure 3- 19 Input Point Interface
Figure 3-20 Distance Measurement
(5) Distance measurement
Distance measurement is used to measure the actual distance between two points. Click Measure → Distance Measurement in turn (Figure 3-20), select two points in the map window, and click in the toolbar to get the measurement result.
(6) View the menu
Click "Drawing" in the menu bar to pop up the drawing menu (Figure 3-2 1). Drawing menu includes multi-selection, click, box selection, zoom in, zoom out, pan, full map, attempt to return, zoom and layer control. Let's introduce the function of each subclass in detail.
Figure 3-2 1 View menu
1) Multiple selections
The multi-selection function is used to select multiple similar elements, such as multiple point elements, line elements or surface elements, and the selected elements will be displayed in different colors.
2) Click.
Click to select one element at a time and the selected elements will be displayed in different colors. When one element is selected and then another element is selected, the previous element will return to its original color.
Tip: In the toolbar, the button is a click button.
3) box selection
The box selection function is used to select all the same elements within the rectangular range at one time. Click the "box selection" function, select a position on the screen, and then move the stylus to ensure that the stylus does not leave the screen during the process. In the process of moving, we will see a rectangular box. When the stylus is released, all elements in the rectangular box will be selected.
4) Zoom in
Zoom in on the map scale, and the button on the toolbar is the zoom-in function.
5) contraction
Reduce the scale of the map, and the button on the toolbar is the zoom-in function.
6) Translation
Move the map, and the button in the toolbar is the move function.
7) Full map
The whole map is displayed on the screen, and the buttons in the toolbar are the function of the whole map.
8) Rear view
Return to the previous view, and the button in the toolbar is the view return function.
9) scale
Quickly select a map scale. Clicking "Zoom" will pop up a submenu. After selecting the required scale in the submenu, the map will be converted to the scale size just selected.
10) layer control
Layer control is used to manage the layers in the current project, and the button on the toolbar is the layer control function. Click "Layer Control" to open the "Layer Control" window, as shown in Figure 3-22. The contents of the window are introduced in turn below.
Figure 3-22 Layer Control
① List name. The top column is the list name. The format of "Layer Name" is * * @ * *, with the layer name before @ and the file name after @, that is, the file where the layer is located; "Type" * * * There are three types: point, line and surface; "Visible" refers to whether the layer is displayed in the map; "Edit" refers to whether a layer is in editing status, and only one layer can be edited at a time. "Optional" refers to whether the data in the layer can be selected.
② Layer information. Below the list name is the layer information.
③ Move the function menu. There are four buttons under the layer information, top, up, down and bottom. Among them, "top layer" means moving the layer to the top layer, "up" means moving the layer up one layer, "down" means moving the layer down one layer, and "bottom layer" means moving the layer to the bottom layer. Generally speaking, you should put the point at the top and the face at the bottom.
④ Layer style. Next to the Layer List, there is a Layer Style button. Select a layer and click "Layer Style" to open the layer style window. Different types of layers have different styles, which will be introduced in the next section.
Five options. Click the "Options" button in the lower right corner to pop up the options menu. See table 3-6 for the function introduction of each menu item.
6 exit. Exit the layer control interface.
1 1) point layer style
Select a point layer in the layer list and click "Layer Style" to open the point layer style window.
Symbol color: change the display color of the point, click on the rectangular box at the back to pop up the color selection window. After selecting, click OK in the upper right corner.
Symbol size: change the size of the point and enter the corresponding number in the rectangular box at the back. Digital input needs to click the bottom button, and so does the following digital input.
Table 3-6 Options Menu Functions
Symbol Angle: Change the rotation angle of the point symbol.
Text filtering: If the dimension text overlaps the point and there is no other position to change, the dimension text will not be displayed.
Text avoidance: If the label text overlaps with the point, the label will automatically change its position.
Fixed size: after selection, the symbol size is fixed and does not change with the change of map scale.
Layer Transparency Settings: Use the slider below to set the transparency of the layer.
Note: After setting the layer style, you must click the "Set Style" button to take effect.
(7) Navigation function
RealMap software supports navigation function and can easily navigate to the target point. Click "Measure" in the menu bar and select "GPS Navigation" in the pop-up menu, as shown in Figure 3-23 below.
Figure 3-23 GPS navigation
RealMap provides two navigation functions, one is to navigate to any point, and the other is to navigate to the selected target. The following two methods are introduced respectively.
1) Navigate to any point.
On the menu bar, click Measure →“GPS Navigation → Navigate to any point.
After clicking, click anywhere on the map and the navigation interface will pop up. The navigation interface consists of two parts-electronic compass and text prompt. The direction pointed by the red arrow in the electronic compass is the direction of the target point, and the text prompt shows the direction difference and linear distance between the current position and the target position.
2) Navigate to the selected target.
On the menu bar, click Survey →“GPS Navigation → Navigate to the selected target. After clicking, select the target point on the map. After selection, a navigation window will pop up.
Note: To navigate to the selected target, you must select a target point. If not selected, a prompt box will pop up.
(8) Data export and import
1) data import
Convert spreadsheet (xls) to pm2:
① Click Tools in the menu bar and select Excel to pm2 (as shown in Figure 3-24).
② The following dialog box pops up (Figure 3-25). There are two coordinate systems: longitude and latitude coordinates and plane coordinates. Coordinate magnification is also divided into two values: 0.0 1 and 0.00 1. According to the data in Excel table, judge the type of coordinate system. If plane coordinates are selected, there are two options for coordinate magnification: 0.0 1 and 0.00 1. In the column of X value in the table, the coordinate magnification is 0.00 1 if the integer is 8 digits, and 0.0 1 if it is 6 digits. Select various field names corresponding to Excel tables in the east and north coordinate columns.
Figure 3-24 Data Import
Figure 3-25 Excel to pm2
Figure 3-26 Data Export
Data conversion succeeded.
2) Export of data
Pm2 is exported as a csv spreadsheet (as shown in Figure 3-26).
Please note that this feature is not available when the dataset is open.
Click Tools → Data Transformation Tool→ "(PM2→ CSV), and then click Export.