# Geospatial information

Several different sensors include geospatial information in the dataset metadata describing the location of the sensor at the time of capture.

**Coordinate reference systems**\
The Scanalyzer system itself does not have a reliable GPS unit on the sensor box. There are 3 different coordinate systems that occur in the data:

* Most common is EPSG:4326 (WGS84) USDA coordinates
* Tractor planting & sensor data is in UTM Zone 12
* Sensor position information is captured relative to the southeast corner of the Scanalyzer system in meters

![](https://cloud.githubusercontent.com/assets/464871/15622807/5e86cb98-2432-11e6-901d-967d6ac0f70d.png)

EPSG:4326 coordinates for the four corners of the Scanalyzer system (bound by the rails above) are as follows:

* **NW**: 33° 04.592' N, -111° 58.505' W
* **NE**: 33° 04.591' N, -111° 58.487' W
* **SW**: 33° 04.474' N, -111° 58.505' W
* **SE**: 33° 04.470' N, -111° 58.485' W

In the trait database, this site is named the ["MAC Field Scanner Field"](https://terraref.ncsa.illinois.edu/bety/sites/6000000001) and its bounding polygon is ["POLYGON ((-111.9747967 33.0764953 358.682, -111.9747966 33.0745228 358.675, -111.9750963 33.074485715 358.62, -111.9750964 33.0764584 358.638, -111.9747967 33.0764953 358.682))"](https://terraref.ncsa.illinois.edu/bety/api/v1/sites?key=9999999999999999999999999999999999999999\&id=6000000001)

**Scanalyzer coordinates**\
Finally, the Scanalyzer coordinate system is right-handed - the origin is in the SE corner, X increases going from south to north, and Y increases from east to the west.

In offset meter measurements from the southeast corner of the Scanalyzer system, the extent of possible motion for the sensor box is defined as:

* **NW**: (207.3, 22.135, 5.5)
* **SE**: (3.8,    0, 0)  

*Scanalyzer -> EPSG:4326*\
1\. Calculate the UTM position of known SE corner point 2. Calculate the UTM position of the target point, using SE point as reference 3. Get EPSG:4326 position based on UTM

**MAC coordinates**\
Tractor planting data and tractor sensor data will use UTM Zone 12.

*Scanalyzer -> MAC*\
Given a Scanalyzer(x,y), the MAC(x,y) in UTM zone 12 is calculated using the linear transformation formula:

```
ay = 3659974.971; by = 1.0002; cy = 0.0078;
ax = 409012.2032; bx = 0.009; cx = - 0.9986;
Mx = ax + bx * Gx + cx * Gy
My = ay + by * Gx + cy * Gy
```

Assume `Gx = -Gx'`, where `Gx'` is the Scanalyzer X coordinate.

*MAC -> Scanalyzer*

```
Gx = ( (My/cy - ay/cy) - (Mx/cx - ax/cx) ) / (by/cy - bx/cx)
Gy = ( (My/by - ay/by) - (Mx/bx - ax/bx) ) / (cy/by - cx/bx)
```

*MAC -> EPSG:4326 USDA*\
We do a linear shifting to convert MAC coordinates in to EPSG:4326 USDA

```
Latitude: Uy = My - 0.000015258894
Longitude: Ux = Mx + 0.000020308287
```

**Sensors with geospatial metadata**

* stereoTop
* flirIr
* co2
* cropCircle
* PRI
* scanner3dTop
* NDVI
* PS2
* SWIR
* VNIR

**Available data**\
\&#xNAN;*All listed sensors*

```
"gantry_system_variable_metadata": {
      "time": "08/17/2016 11:23:14",
      "position x [m]": "207.013",
      "position y [m]": "3.003",
      "position z [m]": "0.68",
      "speed x [m/s]": "0",
      "speed y [m/s]": "0.33",
      "speed z [m/s]": "0",
      "camera box light 1 is on": "True",
      "camera box light 2 is on": "True",
      "camera box light 3 is on": "True",
      "camera box light 4 is on": "True",
      "y end pos [m]": "22.135",
      "y set velocity [m/s]": "0.33",
      "y set acceleration [m/s^2]": "0.1",
      "y set decceleration [m/s^2]": "0.1"
    },
```

*stereoTop*

```
"sensor_fixed_metadata": {
      "cameras alignment": "cameras optical axis parallel to XAxis, perpendicular to ground",
      "optics focus setting (both)": "2.5m",
      "optics apperture setting (both)": "6.7",
      "location in gantry system": "camera box, facing ground",
      "location in camera box x [m]": "0.877",
      "location in camera box y [m]": "2.276",
      "location in camera box z [m]": "0.578",
      "field of view at 2m in X- Y- direction [m]": "[1.857 1.246]",
      "bounding Box [m]": "[1.857     1.246]",
    },
```

cropCircle

```
"sensor_fixed_metadata": {
      "location in gantry system": "camera box, facing ground",
      "location in camera box x [m]": "0.480",
      "location in camera box y [m]": "1.920",
      "location in camera box z [m]": "0.6",
    },
```

*co2Sensor*

```
"sensor_fixed_metadata": {
      "location in gantry system": "camera box, facing ground",
      "location in camera box x [m]": "0.35",
      "location in camera box y [m]": "2.62",
      "location in camera box z [m]": "0.7",
    },
```

*flirIrCamera*

```
"sensor_fixed_metadata": {
      "location in gantry system": "camera box, facing ground",
      "location in camera box x [m]": "0.877",
      "location in camera box y [m]": "1.361",
      "location in camera box z [m]": "0.520",
      "field of view x [m]": "1.496",
      "field of view y [m]": "1.105",
    },
```

*ndviSensor*

```
"sensor_fixed_metadata": {
      "location in gantry system": "top of gantry, facing up, camera box, facing ground",
      "location in camera box x [m]": "0.33",
      "location in camera box y [m]": "2.50",
    },
```

*priSensor*

```
"sensor_fixed_metadata": {
      "location in gantry system": "top of gantry, facing up, camera box, facing ground",
      "location in camera box x [m]": "0.400",
      "location in camera box y [m]": "2.470",
    },
```

*SWIR*

```
"sensor_fixed_metadata": {
      "location in gantry system": "camera box, facing ground",
      "location in camera box x [m]": "0.877",
      "location in camera box y [m]": "2.325",
      "location in camera box z [m]": "0.635",
      "field of view y [m]": "0.75",
      "optics focal length [mm]": "25",
      "optics focus apperture": "2.0",
    },
```

**field scanner plots**

There are 864 (54\*16) plots in total and the plot layout is described in the [plot plan](https://docs.google.com/spreadsheets/d/1QQaWc0UaQQKfEtnSO1G2za8tKU2huC0_VYMBqm5CKAo) table.

| dimension           | value |
| ------------------- | ----- |
| # rows              | 32    |
| # rows / plot       | 2     |
| # plots (2 rows ea) | 864   |
| # ranges            | 54    |
| # columns           | 16    |
| row width (m)       | 0.762 |
| plot length (m)     | 4     |
| row length (m)      | 3.5   |
| alley length (m)    | 0.5   |

The boundary of each plot changes slightly each planting season. The scanalyzer coordinates of each row and each range of the two planting seasons is available in the [field book](https://docs.google.com/spreadsheets/d/1eQSeVMPfrWS9Li4XlJf3qs2F8txmddbwZhjOfMGAvt8/edit#gid=883764630). The scanalyzer coordinates of each plot are transformed into the (EPSG:4326) USDA coordinates using the equations above. After that, a polygon of each plot can be generated using ST\_GeomFromText funtion and inserted into the BETYdb through SQL statements.

An [Rcode](https://github.com/terraref/computing-pipeline/blob/master/scripts/geospatial/field_scanner_plots.R) is available for generating SQL statements based on the scanalyzer coordinates of each plot, which takes range.csv and row\.csv as standard inputs.

The range.csv should be in the following format:

| range | x\_south | x\_north |
| ----- | -------- | -------- |
| 1     | ...      | ...      |
| 2     | ...      | ...      |
| 3     | ...      | ...      |
| ...   | ...      | ...      |

And the row\.csv should look like:

| row | y\_west | y\_east |
| --- | ------- | ------- |
| 1   | ...     | ...     |
| 2   | ...     | ...     |
| 3   | ...     | ...     |
| ... | ...     | ...     |

The output will be something look like:

```
INSERT INTO sites (sitename, geometry) VALUES ( 'MAC Field Scanner Field Plot 1 Season 2',
ST_GeomFromText('POLYGON((-111.975049874375 33.0745312921391 353, -111.975033517034 33.0745313124814 353, 
-111.975033529346 33.0745670737771 353, -111.975049886694 33.0745670534346 353, -111.975049874375 
33.0745312921391 353))', 4326));
```