Background

The Urban Sky microballoon is a small lighter-than-air balloon system capable of carrying a variety of payload systems to the stratosphere or upper atmosphere.

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<aside> 💡 The metadata and sensor model are shared between all current Urban Sky L1B products, and collectively describe how 3D world points get mapped into the sensor coordinates for accessing pixel values from an L1B image.

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Metadata files

One metadata file per image

Each metadata file is a two-line CSV file, with one line for column labels and the other line for actual values. Header lines for all CSV files are identical. The included metadata include:

Name	Description
Latitude	Latitude of the sensor; degrees
Longitude	Longitude of the sensor; degrees
Altitude	Altitude of the sensor; MSL meters
Pitch	Pitch of the sensor; degrees
Roll	Roll of the sensor; degrees
Heading	Heading of the sensor; degrees. Due north is 0 degrees, with increasing values corresponding to counter-clockwise such that due west is 90 degrees.
FocalLengthMeters	Focal length of the optics; meters.
PixelSizeMetersX	Size of a single pixel in the x dimension; meters.
PixelSizeMetersY	Size of a single pixel in the y dimension; meters.
DistortionK1	Optical geometric distortion term applied to $r^2$
DistortionK2	Optical geometric distortion term applied to $r^4$

One metadata file for whole collect

For customer convenience, we also provide a single CSV file with the metadata for all images combined. The main difference is an additional column:

Name	Description
Name	Image filename to which this CSV line corresponds

World file

Each image has an associated world file. See here for more details on world files. These world files can be used by an aware GIS application, such as QGIS or ArcGIS, to place and warp the image to its approximate location on a map. These world files are provided for information purposes only, to help a customer visualize roughly where the L1B images are located on a map. They can also be used to help a customer verify that they are interpreting our Sensor Model correctly — when using our Sensor Model to project a 3D world point covered by an L1B image, the Sensor Model should give a valid pixel.