Using parallax in remote sensing to determine cloud feature height

A method of determining the height above ground of an object in the sky, comprising:

• collecting from a position above the surface of the Earth light energy coming from a first direction;
• collecting from a position above the surface of the Earth light energy coming from a second direction, wherein the second direction is not parallel to the first direction;
• comparing the light energy from the first direction and the second direction to determine when an object in the sky is encountered, and determining a measure of the difference between the light energy from the two directions when the object is encountered;
• and
• calculating the height above Earth of the object based on the measure of the difference;
• wherein the comparing operation includes:
• comparing the light energy from the first direction and the second direction to determine when a leading edge of an object in the sky is encountered, and determining a measure of the difference between the light energy from the two directions when the leading edge is encountered;
• comparing the light energy from the first direction and the second direction to determine when a lagging edge of an object in the sky is encountered, and determining a measure of the difference between the light energy from the two directions when the lagging edge is encountered;
• and wherein the calculating operation includes:
• calculating the height of the leading edge of the object based on the measure of the difference between the light energy from the two directions when the leading edge is encountered;
• and
• calculating the height of the lagging edge of the object based on the measure of the difference between the light energy from the two directions when the lagging edge is encountered.

A method of determining the height above ground of an object in the sky, comprising:

• collecting from a position above the surface of the Earth light energy coming from a first direction;
• collecting from a position above the surface of the Earth light energy coming from a second direction, wherein the second direction is not parallel to the first direction;
• comparing the light energy from the first direction and the second direction to determine when an object in the sky is encountered, and determining a measure of the difference between the light energy from the two directions when the object is encountered;
• and
• calculating the height above Earth of the object based on the measure of the difference;
• wherein the determining operation of the comparing operation includes determining the number of pixels on the ground that can be seen in one of the first and second directions that cannot be seen on the ground in the other of the directions.

A method of determining the height of a cloud, comprising:

• providing a pair of radiant energy sensors at a height greater than the cloud, the sensors being directed toward the cloud at a small parallax angle relative to each other, the parallax angle being less than 5 degrees;
• receiving radiant energy with the sensors;
• and
• comparing the radiant energy received by the two sensors to determine the height of the cloud.

A method of determining the height above ground of an opaque cloud in the sky, comprising:

• providing a multi-band line scanning imager with first and second SWIR sensor bands that are aligned in such a way that the two bands are parallel in the cross-scan direction, but non-parallel with a small, but non-zero, parallax angle in the in-scan direction;
• collecting radiant energy with the imager from a moving above-ground platform that is further from the ground than an opaque cloud;
• forming separate ortho-rectified, co-registered SWIR images, based on collected sensor data from the first and second bands;
• forming separate ortho-rectified, co-registered classification images, based on the first and second SWIR images, that classify each pixel within each image as either opaque cloud, snow/ice, or other;
• comparing the first and second classification images to identify in-scan segments of pixels where corresponding pixels in both of the first and second classification images has been classified as opaque cloud, leading to further classification of these pixels as opaque cloud interior pixels;
• comparing the first and second classification images to identify in-scan segments of pixels where corresponding pixels in one of the first and second said classification images has been classified as opaque cloud and the corresponding pixels in the other of the first and second classification images has been classified as snow/ice or other, leading to further classification of these pixels as opaque cloud edge pixels;
• and
• based on the opaque cloud edge pixels and the opaque cloud interior pixels, determining the height above ground of the opaque cloud edge pixels.