1. HYDROGEOLOGY OF THE ZACATÓN CAVE SYSTEM
Building a Geodatabase from (below) the Ground Up
Marcus Gary
Department of Geological Sciences
The University of Texas at Austin

2. Some of the Research Goals at the
About the Caves
The cenote Zacatón is the largest flooded sinkhole (cenote) in the world.
Hydrothermal Karst System
Some of the Research Goals at the
Zacatón System
Interpret the geological history that formed the caves
Create a 3-D geodatabase

3. Cenotes of Sistema Zacatón

4. Collect lots of field data and put all the information into true 3-dimensional context
Rock
Samples
Biological
Samples
Water
Samples
3-D Imaging using LADAR

5. LAser Detection And Ranging
What is LADAR?
LAser Detection And Ranging or
LAser raDAR
Similar to LIDAR, but a bit different
Light Intensity Distance And Ranging
LIDAR
LADAR
Uses laser scanner
Moving platform
“Downlooking” only
Centimeter accuracy
Uses laser scanner
Static platform
Full range of “vision”
Millimeter accuracy

6. LADAR Instrument Pan-Tilt Scanner: Riegl LMS-25
Frame Rate: 90 min / frame
Range: 150 m
Accuracy: 20 mm
Approx. 6,000,000 points/frame
FOV +90 / -45 degrees

7. LADAR output: what you get
Reflectance Intensity (greyscale, typ )
Range Data
raw data typ. Angle, Angle, Distance
Plots of range data are known as “Point Clouds”
Plots can be 3D or 2D (e.g. a JPEG image in which x & y spacing represents pitch and yaw angular increment and color represents scaled range)
Spectral Data (optional – RGB intensity)
NOTE** A single LADAR data frame represents a “2-1/2 D” view of the world

8. 1. Drill and set benchmark
A Total Station survey instrument was used to precisely georeference benchmarks that are the origin of each LADAR scan.
2. Shoot survey with Total Station
3. Record distance and angles and process data
(easting, northing, elevation)

9. Lots of Benchmarks were surveyed
LADAR scanning benchmark
Water Level benchmark
Intermediate benchmark

10. A few scanning locations

11. Range image of Zacatón created by LADAR instrument software

12. Color Depth Map of Range Image of Cave
Cueva Cuarteles, Rancho la Azufrosa, Tamps., Mexico
1,500,000 3D data points

13. 360-deg Intensity Image of Cave: 750v x 2000h

14. ZACATÓN

15. First shot at making a TIN of the scene

16. LADAR can even image a person
Some problems occur when processing TINs from LADAR data
(mesh from origin, not in Z-direction)
LADAR can even image a person
TIN man
Intensity Image

17. Data Processing
Lots of data – need REALLY BIG computer
Texas Advanced Computing Center (TACC) has a 24-processor SGI Onyx2 and the 3-D visualization lab to process and view the entire dataset (and more).

18. Future 3-D data collection in different medians
Geophysical resistivity data of rock structures between sinkholes
LADAR data of the surface features (already acquired).
SONAR data of the underwater voids (caves)