DAQ-A-SD User Manual
This page describes the DAQ-A-SD
The DAQ-A-SD is an aerodynamic PPK data logger containing GNSS (GPS) and IMU position sensors, with a user-accessible micro SD card for saving the data log. An integrated, downwelling SPECTROMETER records the changing ambient light spectrum (340 - 1010 nm) to assist with calibrating Survey3 camera images. There is a USB port for power input, an RGB LED status button and two Survey3 camera connection ports.
The SD model can measure bright overhead (D = downwelling) light sources, such as the sun. It has been designed to not oversaturate under super bright sunlight, perfect for outdoor use. The relative radiometric calibration keeps the wavelength to wavelength measurements consistent regardless of the intensity of the changing ambient light. The SD relative illumination spectrometer is not calibrated for irradiance (W/m^2) so it cannot measure the amount of light intensity (power) change.
When the spectrometer log data is used with images of our reflectance reference targets the resulting calibrated pixel data will be in the units of percent reflectance. As the ambient light changes, any radiometric differences are corrected for, meaning multispectral indices such as NDVI are maintained. Radiometric differences in the overall light intensity and spectrum are calibrated and comparable across different locations and time.
The built in white glass diffuser is a cosine corrector, which has a ~180 degree capture angle. Even when tilted the measurements should remain consistent. The DAQ-A-SD can be used at any angle, but if the GNSS location data is important to record, please keep in mind that tilting away from the sky will reduce the GNSS location accuracy.
Power (5V) is supplied to the DAQ-A depending on how you have it connected. You can EITHER supply power input to the DAQ-A micro USB port OR into either of the Survey3 camera ports. Do not send power into BOTH the micro USB and the Survey3 camera port(s).
Once power is connected the DAQ-A will boot up. It can take several minutes from when the power is first connected to when the button LED turns red, so please be patient. The system is usable when the button LED is green. The GNSS inside the DAQ-A has 2 LEDs located on the top, a faint green/yellow LED for power and a flashing blue LED once it has a satellite lock. Each Survey3 camera will beep 6 times once the GNSS has a lock.
The DAQ-A is recording when the button LED is green
Adjusting DAQ-A-SD Settings
You can adjust the DAQ-A-SD device settings by editing the micro SD configuration file.
To Start/Stop Image Capture
By default the auto-start image capture parameter will be off, so triggering must be started manually. You can edit the configuration file to turn auto-start on/off.
The RGB button can be clicked with a short press action to start the image capturing sequence. If the interval parameter is greater than 0, the trigger signal will be sent at the interval rate (in seconds). If the interval is 0 then one trigger will be sent per button click. When the image capturing interval is active the LED will pulse (fade off-on-off) green. The interval value can be edited in the configuration file.
To Start/Stop Data Logging
Performing a long button press (more than 5 seconds) will start or stop the data logging. The button LED will change from logging ON (GREEN) to logging OFF (RED) or vice versa when pressed and released.
Prior to removing power to the DAQ-A-SD you MUST disable logging, or there is a good chance the micro SD could become corrupted. This is because the micro SD card is constantly being written to when saving the sensor data. If the current log becomes corrupted there is nothing that can be done to repair it.
Always stop the data logging (red LED) before disconnecting power to the DAQ-A-SD!​
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