Enabling Shallow Water Flight on Slocum Gliders Chip Haldeman, David Aragon, Hugh Roarty, Scott...
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Transcript of Enabling Shallow Water Flight on Slocum Gliders Chip Haldeman, David Aragon, Hugh Roarty, Scott...
![Page 1: Enabling Shallow Water Flight on Slocum Gliders Chip Haldeman, David Aragon, Hugh Roarty, Scott Glenn, and Josh Kohut Rutgers University Blue - < 9 m.](https://reader036.fdocuments.net/reader036/viewer/2022062804/56649e2c5503460f94b1bf79/html5/thumbnails/1.jpg)
Enabling Shallow Water Flight on Slocum Gliders
Chip Haldeman, David Aragon, Hugh Roarty, Scott Glenn, and Josh Kohut
Rutgers University
Blue - < 9 m
![Page 2: Enabling Shallow Water Flight on Slocum Gliders Chip Haldeman, David Aragon, Hugh Roarty, Scott Glenn, and Josh Kohut Rutgers University Blue - < 9 m.](https://reader036.fdocuments.net/reader036/viewer/2022062804/56649e2c5503460f94b1bf79/html5/thumbnails/2.jpg)
Autonomous Platforms
Very broad…includes a wide variety of applications
![Page 3: Enabling Shallow Water Flight on Slocum Gliders Chip Haldeman, David Aragon, Hugh Roarty, Scott Glenn, and Josh Kohut Rutgers University Blue - < 9 m.](https://reader036.fdocuments.net/reader036/viewer/2022062804/56649e2c5503460f94b1bf79/html5/thumbnails/3.jpg)
In our field:Autonomous Platforms
Wave GliderREMUS
![Page 4: Enabling Shallow Water Flight on Slocum Gliders Chip Haldeman, David Aragon, Hugh Roarty, Scott Glenn, and Josh Kohut Rutgers University Blue - < 9 m.](https://reader036.fdocuments.net/reader036/viewer/2022062804/56649e2c5503460f94b1bf79/html5/thumbnails/4.jpg)
Seaglider
APEX Floats
Spray Glider
Autonomous Platforms – buoyancy driven
Slocum glider – only shallow water capable glider
Shallow water pump (4-30 m water depth)
![Page 5: Enabling Shallow Water Flight on Slocum Gliders Chip Haldeman, David Aragon, Hugh Roarty, Scott Glenn, and Josh Kohut Rutgers University Blue - < 9 m.](https://reader036.fdocuments.net/reader036/viewer/2022062804/56649e2c5503460f94b1bf79/html5/thumbnails/5.jpg)
Shallow Water Sampling Issues
“Dredging”
“Bottom Sampling”
UD_275 “OTIS”
RU28
Pressure
Measured water depth
Pressure + raw altitude
![Page 6: Enabling Shallow Water Flight on Slocum Gliders Chip Haldeman, David Aragon, Hugh Roarty, Scott Glenn, and Josh Kohut Rutgers University Blue - < 9 m.](https://reader036.fdocuments.net/reader036/viewer/2022062804/56649e2c5503460f94b1bf79/html5/thumbnails/6.jpg)
Shallow Water Sampling Issues
Why is this bad?
1. Data quality
– affects vertical and spatial resolution. Glider is still sampling, so there is plenty of data, but not where you want it.
2. Platform Risk
-- Sediment buildup in nosecone results in loss of buoyancy. Can’t float, can’t fly. Ejection weight?
-- Sediment in nosecone grinds between pump and diaphragm, causing leak and ending mission…or loss of the platform.
*Tip - Plug the nosecone for shallow coastal flights
![Page 7: Enabling Shallow Water Flight on Slocum Gliders Chip Haldeman, David Aragon, Hugh Roarty, Scott Glenn, and Josh Kohut Rutgers University Blue - < 9 m.](https://reader036.fdocuments.net/reader036/viewer/2022062804/56649e2c5503460f94b1bf79/html5/thumbnails/7.jpg)
• This leaves a short window to obtain a hit during about 3 cycles or 12 seconds. Altimeter produces a hit every ~2 cycles.
OBTAINING HITS IN VERY SHALLOW WATER
REJECTED REJECTEDACCEPTED...
but 2 hits are required
Considered “on surface” or “too soon after inflection”
Too close to bottom (below minimum altimeter value)
![Page 8: Enabling Shallow Water Flight on Slocum Gliders Chip Haldeman, David Aragon, Hugh Roarty, Scott Glenn, and Josh Kohut Rutgers University Blue - < 9 m.](https://reader036.fdocuments.net/reader036/viewer/2022062804/56649e2c5503460f94b1bf79/html5/thumbnails/8.jpg)
• Altimeter filter: m_water_depth [n] = m_depth [n] + m_raw_altitude [n-1]Normally adds ~ 1 m to glider’s water depth calculation
Pitch angle depth correction
ALTIMETRY: TAKING GROUND TRUTHING LITERALLY
![Page 9: Enabling Shallow Water Flight on Slocum Gliders Chip Haldeman, David Aragon, Hugh Roarty, Scott Glenn, and Josh Kohut Rutgers University Blue - < 9 m.](https://reader036.fdocuments.net/reader036/viewer/2022062804/56649e2c5503460f94b1bf79/html5/thumbnails/9.jpg)
Glider’s water depth = altitude (filtered) + glider
depth
Water depth = altitude + glider depth
Actual water depth corrected for pitch
• Actual depth is 21 m according to pitch corrected pressure sensor• Non-filtered pings show depth at about .3 m shallower, filtered pings show depth about 1.2 m deeper• In this example our altimeter, with the filter, is creating depths about 1.2 m deeper than actual.
ALTIMETRY: FINDING THE WRONG BOTTOM
![Page 10: Enabling Shallow Water Flight on Slocum Gliders Chip Haldeman, David Aragon, Hugh Roarty, Scott Glenn, and Josh Kohut Rutgers University Blue - < 9 m.](https://reader036.fdocuments.net/reader036/viewer/2022062804/56649e2c5503460f94b1bf79/html5/thumbnails/10.jpg)
As glider approaches bottom, hits below u_min_altimeter setting are rejected, but surface reflections are seen and accepted as “good”…so glider attempts to descend through ~10 m of sediment
10 m
10 m
SURFACE REFLECTIONS
REJECTED
“on surface/not diving” or hasn’t met “post-inflection time” requirements. Hits considered “good”, but rejected
ACCEPTED
![Page 11: Enabling Shallow Water Flight on Slocum Gliders Chip Haldeman, David Aragon, Hugh Roarty, Scott Glenn, and Josh Kohut Rutgers University Blue - < 9 m.](https://reader036.fdocuments.net/reader036/viewer/2022062804/56649e2c5503460f94b1bf79/html5/thumbnails/11.jpg)
How do we fix it?
Software solution, developed and tested at Rutgers, modifies default deepwater flight settings to enable shallow water flight. Confident of flight in 8 m of water…possibly as shallow as 6 m.
-- Obtaining valid altimetry in very shallow water - several default settings modified to allow more altimetry through
-- To avoid reflections, limit range of altimeter to less than water depth.
Shallow Water Sampling Issues
![Page 12: Enabling Shallow Water Flight on Slocum Gliders Chip Haldeman, David Aragon, Hugh Roarty, Scott Glenn, and Josh Kohut Rutgers University Blue - < 9 m.](https://reader036.fdocuments.net/reader036/viewer/2022062804/56649e2c5503460f94b1bf79/html5/thumbnails/12.jpg)
Pushing the envelope – very shallow water (6-7 m) flight
• 1-2 bottom solutions per dive; approx. 9 cycles or ~ 30 seconds• Flight in depths shallower than above will likely require a change in flight
characteristics (pitch angle, pump throw, H stability) to slow flight and allow more valid altimetry. How do we address altimetry reflection issue?
![Page 13: Enabling Shallow Water Flight on Slocum Gliders Chip Haldeman, David Aragon, Hugh Roarty, Scott Glenn, and Josh Kohut Rutgers University Blue - < 9 m.](https://reader036.fdocuments.net/reader036/viewer/2022062804/56649e2c5503460f94b1bf79/html5/thumbnails/13.jpg)
•Slocum gliders are capable of flight in shallow water, 4-30 m
•Software fix modifies deepwater flight settings to enable shallow water flight
•Bottom impacts and data degradation avoided
![Page 14: Enabling Shallow Water Flight on Slocum Gliders Chip Haldeman, David Aragon, Hugh Roarty, Scott Glenn, and Josh Kohut Rutgers University Blue - < 9 m.](https://reader036.fdocuments.net/reader036/viewer/2022062804/56649e2c5503460f94b1bf79/html5/thumbnails/14.jpg)
### alt.mi Shallow water (<15 m) altimetry coefficients### David Aragon, Chip Haldeman, Rutgers University ### Account for shallow water; need enough good hitssensor: u_reqd_depth_at_surface(m) 2sensor: u_alt_min_post_inflection_time(sec) 4.0 sensor: u_alt_min_depth(m) 1.0sensor: u_min_altimeter(m) 1.5 ### Set this to less than actual water depth to avoid reflectionssensor: u_max_altimeter(m) 6.0 ### Reduces filtered altimetrysensor: u_alt_reqd_good_in_a_row(nodim) 1sensor: u_alt_filter_enabled(bool) 0sensor: u_alt_reduced_usage_mode(bool) 0 ### Avoids bug in code; likely fixed but untested...sensor: m_altitude_rate(m/s) -1sensor: u_sound_speed(m/s) 1510.0 ### Keeps previous depth if new one not attained (2 yos)sensor: u_max_water_depth_lifetime(yos) 2### Attempts to limit max slope of bottom (use cautiously)sensor: u_max_bottom_slope(m/m) 3.0 ### Set this to get around false hits at depth, but use caution!!!sensor: u_min_water_depth(m) 0 sensor: u_max_water_depth(m) 2000
alt.mi