How to use the advanced layer visualization in Pix4Dfields

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General information of a layer

Click on the layer to display its general information, to change the color mode, to change the range, and the contrast of a histogram.

Color mode

Color mode for vegetation indices

Color mode for terrain

• Grayscale: The index image is colored with shades of gray, where pixels with lowest index value are black and the pixels are brighter with increasing index value. That is the way each raw image per band appears when opened with a standard image viewer application.
• Red-Green: The "standard" view - the color scale ranges from red to green.
• Thermal: This color mode is visualized on the scale of black/purple to yellow/white. This is not a thermal map (i.e it does not represent temperature values)
• Spectral: The color scale goes from blue to red.
• Terrain: This color mode is designed for the Digital Surface Model (DSM) and helps visualize depth change from blue to orange on the scale.

Histogram for Indices

The histogram shows on the x-axis the range of the pixel values in the selected layer; the y-axis shows the frequency of pixels with a specific value. The values displayed on the x-axis, and the number of pixels which have those values (y-axis) will vary depending on the input data, and the vegetation index that you use. See the example below:

Histogram of a vegetation index (e.g. NDVI)Histogram of a Digital Surface Model

Histogram of a vegetation index (e.g. NDVI)

Histogram of a Digital Surface Model

For more information about vegetation indices: Generate a vegetation index.

The dynamic range

You can set up the minimum and maximum value of the histogram to adjust the dynamic range.

Dynamic range for vegetation indices (e.g. NDVI)

Dynamic range for Digital Surface Model

Changing the range in the x-axis of the histogram (index value) enables you to concentrate on certain values which give you more insights into the condition of your fields. For example, in the right image below, a range for the NDVI has been given, enabling you to better distinguish between stressed and healthy areas.

NDVI as an example without using the dynamic range (default settings)

NDVI as an example using the dynamic range (minimum and maximum values)

NDVI as an example using the dynamic range (one value)

Display modes

Pix4Dfields offers two display modes of the pixels with data values below and above the specified color range: transparent and solid.

• Transparent mode displays all areas with pixel values outside the given range as transparent.
• Solid mode displays areas below of the given range with one color and the values above the selected range with another color. The colors which the solid mode displays vary between the color modes (Red-Green, Spectral, Thermal and Grayscale) selected for each layer. For example, if the color mode Red-Green is used, the values above the selected range will be displayed as green, and the values below the range will be displayed as red.

NDVI as an example with transparent mode

NDVI as an example with solid mode

Histogram equalization

Pix4Dfields allows you to perform histogram equalization. Histogram equalization enhances contrast by stretching out the most frequent intensity values in the histogram.

NDVI as an example with equalization

NDVI as an example without equalization

Dimensions

The dimensions (in pixels) of a layer depends on the area covered by the input images and the GSD.

GSD

The Ground Sampling Distance (GSD) is the distance between two consecutive pixel centers measured on the ground. The higher the GSD value, the fewer details that are visible on the ground (less spatial resolution). The GSD value and spatial resolution are closely related to the altitude of the drone flight and camera parameters. The GSD can be determined by the settings in the advanced processing options. For more information about GSD: Orthomosaic GSD in Pix4Dfields

File Size

The file size depends on the number of pixels and the number of bits of your images.

Data Type

Pix4Dfields supports TIFF images with 8, 10, 12, 14, and 16 bit integers, and floating-point as inputs. For more information: Inputs and Outputs

Coordinate System

Shows the coordinate system of the input data.

Bands

This section displays the bands that your sensor has. The order of the bands displayed on Pix4Dfields depends on the Xmp.Camera.BandName tag defined by your camera manufacturer. For more information EXIF and XMP tag information read by Pix4D

Acquisition

Shows the time of acquisition and the duration of your flight. This information is taken from the Exif.GPSInfo.GPSTimeStamp tag of your dataset.

Radiometric Correction Type

The radiometric correction type that Pix4Dfields used on your project can be seen when clicking the corresponding orthomosaic.

Pix4Dfields performs different types of radiometric correction, depending on the availability of the following sources: Image EXIF tags, sunshine sensor, reflectance targets, thermal profile, and weather conditions during the capture. For more information: Radiometric correction in Pix4Dfields