We offer 6 different filter options for the Survey2 cameras ($400 each):
|Visible Light RGB||This camera captures Visible Light RGB color similar to our eyes. Most of the time this camera is used as a reference image to compare with the results from the other cameras, but it can also be used for many other uses such as 3D photogrammetry. The images from this camera can be processed in any ortho-mosaic generating program.
The Survey2 is the newest in our line of simple to use survey cameras. Its 16MP sensor and sharp non-fisheye lens allows you to easily capture aerial media. It captures photos on the default timer trigger or can be sent a PWM signal through the HDMI port (see below). If you supply power to the USB port it will power on and off the camera automatically. Sized similar to a GoPro® Hero these small survey cameras can be attached to your aerial drone platform using our various mounts.This model captures visible light just like our eyes do. A visible light camera for surveying is commonly used for capturing a reference color image that can be used to compare to a NDVI graded one. It can also be used for orthophotography where many photos are combined to generate a 3D model.The Survey2 cameras have a faster interval timer: 2 seconds for JPG mode and 3 seconds for RAW+JPG mode. (Capture speed depends on the speed of the microSD card used, see below for recommended cards). You can also trigger the photo capture using a PWM signal through the HDMI port (see triggering information below).
For best stitching results, we recommend a survey overlap of at least 70% front-lap and 70% side-lap and a maximum 5mph (8kmh) speed for every 65ft (20m) of altitude (AGL) for RAW+JPG mode, and a maximum 10mph (16kmh) speed for every 65ft (20m) of altitude (AGL) for JPG only mode.
|NDVI Red+NIR||This camera has a dual-band filter that captured reflected Red light in the RGB sensor’s red channel and reflected Near Infrared light in the RGB sensor’s blue channel. You can thus use this single camera to compute the NDVI indice, though the contrast in the resulting index image will not be as “accurate” as using the separate Red and NIR camera models. The images from this camera can be processed in any ortho-mosaic generating program.|
|Near Infrared (NIR)||This camera captures the reflected NIR light in the RGB sensor’s red channel. This camera is used in many different indices such as NDVI, ENDVI, SAVI, etc. The images from this camera can only be processed in any ortho-mosaic generating program that uses a shared DSM between image sets (such as Pix4D).|
|Red||This camera captures the reflected Red light in the RGB sensor’s red channel. This camera is used in many different indices (such as NDVI, EVI, SAVI, etc) and to combine with the Green and Blue cameras to make a RGB Visible Light color reference image. The images from this camera can only be processed in any ortho-mosaic generating program that uses a shared DSM between image sets (such as Pix4D).|
|Green||This camera captures the reflected Green light in the RGB sensor’s red channel. This camera is used in many different indices (such as GNDVI, GVI, etc) and to combine with the Red and Blue cameras to make a RGB Visible Light color reference image. The images from this camera can only be processed in any ortho-mosaic generating program that uses a shared DSM between image sets (such as Pix4D).|
|Blue||This camera captures the reflected Blue light in the RGB sensor’s blue channel. This camera is typically used to compute indices such as EVI and to combine with the Red and Green cameras to make a RGB Visible Light color reference image. The images from this camera can only be processed in any ortho-mosaic generating program that uses a shared DSM between image sets (such as Pix4D).|
Please watch the videos below for an example workflow of setting up a survey mission, geo-referencing the captured images and uploading to MAPIR Cloud for post processing:
Post-processing survey photos requires only a few steps but there are many different software packages you can use to get the results you desire.
Capture & Apply GPS Locations to Survey Images
First thing you should do when you receive your camera is set the camera’s time to GPS time. GPS time is 17 seconds faster than UTC time. Go to the camera’s settings and use this site to set to GPS time. If you are triggering the camera via PWM make sure to set the Time Lapse Photo setting to OFF.
Mission planning is based on your aerial platform and what flight controller it is using. The video above shows how to setup a mission with a Pixhawk-based drone and the free Android mission planning application Tower. The flight controller’s log file saved during the mission is used to apply GPS locations to the JPG images, known as geo-referencing the photos. You can watch a video on how to extract the log file from a Pixhawk here using Mission Planner, and this page has links on how to convert the DJI flight logs. Our video above shows how to geo-reference the photos using the converted log file and the program GeoSetter. If you are unable to obtain a log file in a format that GeoSetter can read then we recommend purchasing an external GPS tracker to save your flight path.
Process RAW+JPG Images in Fiji MAPIR Plugin
Once you apply the GPS locations to the JPG images you will want to process the folder of RAW and JPG images with our Fiji MAPIR plugin. This plugin is a pre-processing step to convert the RAW images to TIFFs, copy the EXIF image metadata from the JPGs (including the GPS locations) and correct for the lens vignette. While we recommend only using the processed TIFF images to create your orthomosaic maps (some software will only support the JPGs such as MAPIR Cloud, DroneDeploy, MapsMadeEasy), our plugin will also correct the vignette of the JPGs.
Creating the Ortho-mosaic Images
An ortho-mosaic is a single stitched image containing the many individual photos taken during your survey. Your results will vary though based on the capabilities of the software used to create the ortho image.
Software that is not able to use an image’s GPS data to assist stitching will struggle to create ortho-mosaics of complex subject matter. Complex subject matter are those typically captured when flying over areas where the images captured will look very similar to each other, such as agricultural fields. Software that doesn’t use the GPS data will also have no way to locate the final stitched ortho image onto a map (like Google Earth) because there will be no reference GPS information. We strongly recommend you do not use software that cannot take advantage of the GPS location in the survey images.
There are two options to process your images with GPS information: cloud-based services that do the processing for you or stand-alone programs you run yourself.
Cloud-based packages such as MAPIR Cloud, Drone Deploy, MapsMadeEasy all require you to upload your images to their site and then notify you when the processing is completed. These services vary in how they charge you but the majority have a minimum monthly fee around $100. They also vary in the final results you’ll get from their services, and typically the more expensive “professional” packages provide more outputs with higher cost. Output examples include geo-reference images, DSM maps, KML files and NDVI color-graded images. These cloud-based services often do not support RAW/TIFF files and only work with JPGs, meaning much of the pixel information is changed in the conversion to JPG. They also do not support single band filter cameras for more precise indice/raster calculations, nor reflectance calibration using radiometric ground targets so you will need to do that using additional software. While these cloud-based sites are adding more and more features each month the best option is to process the images using the following dedicated software packages hosted on your own computer.
Two of the top packages used by our customers are Pix4Dmapper and Agisoft Photoscan. These programs are more commonly known as “point cloud” software. They are called this because they look at each and every point, or more specifically each pixel and match up the images. While they can stitch some image sets this way without GPS information, it will greatly reduce your processing time and increase your success rate if you do use geo-referenced photos. Since these programs create a point cloud they can also output .obj, .mtl and .jpeg texture files to be used in 3D model viewers like p3d and sketchfab. The biggest difference between the cloud-based software and a program like Pix4Dmapper is that Pix4Dmapper allows a user to process multiple cameras in a single project and have each ortho-mosaic share the elevation map file. This means that each of the resulting ortho-mosacis are perfectly aligned with each other and if you brought them in as separate layers to Photoshop each similar pixel would be lined up across the layers. Pix4Dmapper also allows you to calibrate the pixel values and process the orthos into an index image (see the next step below) all without leaving their software package. If you’re looking for the most complete software to post process your images you can’t beat the features that Pix4Dmapper offers. These powerful point cloud software packages typically cost about 3x more than the cloud-based services but the additional cost should be easily amortized over time due to the more accurate, consistent results from properly normalized data.
Create Index Images and Apply Color Map (lut)
Once you have the stitched ortho-mosaics you may want to create a colored gradient image to show the indice (NDVI, ENDVI, GNDVI, OSAVI, RDVI, SAVI, etc.) you’re looking for. The NDVI indice is used to show the general “health” of the survey area and is the most common indice created.
As mentioned above, the cloud processing applications (MAPIR Cloud, DroneDeploy, MapsMadeEasy) are only able to process the Visible Light RGB and NDVI model Survey cameras. The NIR camera can also be used if the service is only processing for DVI with the reflected NIR band in the image.
To process the other single-band camera models (Infrared, Red, Green, Blue) you will need to use a program (Pix4Dmapper) that will create the ortho-mosaics of each camera together with the other cameras. This will align them with each other better than any alignment post-processing application will allow for, and is the only way to process an accurate index image from multiple sensors.
Once you create your index image you should calibrate the pixel values with a ground target of known reflectance properties. Calibration allows you to compare multiple surveys over time and is vital in normalizing your data. Both Pix4D and Fiji allow you to read in target data and calibrate your images.
You can also use what we call a “base calibration” in Fiji to calibrate them at an average reflectance and produce very similar results even without ground targets. We create the calibration files based on sampling our many high quality reflectance targets. This allows any user of our cameras to achieve high quality, detailed survey maps with good calibrated normalized data. This procedure is documented in detail HERE.