From 467e85f635d166608e88d71093b004e7c9257c00 Mon Sep 17 00:00:00 2001 From: Pawel Krawczyk Date: Wed, 14 Feb 2024 20:17:04 +0000 Subject: [PATCH] Add Wet Sink testing results --- README.md | 31 +++- wet_sink_crawl.svg | 356 ++++++++++++++++++++++++++++++++++++++++++++ wet_sink_cross1.svg | 349 +++++++++++++++++++++++++++++++++++++++++++ wet_sink_cross2.svg | 356 ++++++++++++++++++++++++++++++++++++++++++++ wet_sink_evel1.svg | 317 +++++++++++++++++++++++++++++++++++++++ 5 files changed, 1408 insertions(+), 1 deletion(-) create mode 100644 wet_sink_crawl.svg create mode 100644 wet_sink_cross1.svg create mode 100644 wet_sink_cross2.svg create mode 100644 wet_sink_evel1.svg diff --git a/README.md b/README.md index 29dc99e..bdc7616 100644 --- a/README.md +++ b/README.md @@ -77,7 +77,7 @@ Bill of materials: #### Barometric pressure -As cave nodes are located through the cave, they have no means of determining their own location as GPS signal is unavailable. Barometric pressure sensor allows to [correlate the pressure](https://en.wikipedia.org/wiki/Barometric_formula) seen by a node with altitude above mean sea level ([AMSL](https://en.wikipedia.org/wiki/Height_above_mean_sea_level)) as long as at least one surface node is equipped with GPS receiver _and_ barometric pressure sensor. The surface node would then operate as the barometric reference for the whole network. With this improvement, the Meshtastic application would see the nodes identified by their depth rather than merely names, e.g.: +As cave nodes are located through the cave, they have no means of determining their own location as GPS signal is unavailable. Barometric pressure sensor allows to [correlate the pressure](https://en.wikipedia.org/wiki/Barometric_formula) seen by a node with altitude above mean sea level ([AMSL](https://en.wikipedia.org/wiki/Height_above_mean_sea_level)) as long as at least one surface node is equipped with GPS receiver _and_ barometric pressure sensor. The surface node would then operate as the barometric/altitude reference for the whole network. With this improvement, the Meshtastic application would see the nodes identified by their depth rather than merely names, e.g.: 1. 0 m relative (surface node) 2. -50 m @@ -91,6 +91,35 @@ Messages sent to the channels could be also identified by the depth of the respe Long, tight crawls are especially challenging for connecting using relay nodes due to relatively short (~10 m max in our tests) radio range and high risk of the nodes being displaced or damaged by cavers moving with bags in confined space. In theory, the nodes could be also connected using a serial cable connected to the USB-C port, which could replace the radio link through the problematic tunnel. The Meshtastic firmware currently supports [serial communications](https://meshtastic.org/docs/configuration/module/serial/) but not exactly for node-to-node links. The length of such a hypothetical link and how it would need to be powered is also unknown. +## Testing + +Initial testing in real-life conditions was performed with [GCRG](https://gcrg.org.uk) in [Wet Sink cave](https://en.wikipedia.org/wiki/Slaughter_Stream_Cave) which offers all typical karst cave features - pitches, chokes, tight squeezes, water. + +1. One "surface" node was placed at the head of entrance pitch. Another one was carried down until signal was lost, which came out to be nearly at the bottom of the next pitch (Mouse pitch). + This covered ~20 m vertically with a horizontal displacement of ~5 m in a choke in the middle. + +![Surface to Mouse pitch](wet_sink_evel1.svg "Surface to Mouse pitch") + +2. Three "cave" nodes were used to create a link through a tight ~30 m long crawl joining the bottom of the Pen Pot pitch with Cross Stream Junction. The crawl is 30-40 cm high + with numerous sharp turns on the way. + +![Tight crawl link](wet_sink_crawl.svg "Tight crawl link") + +3. Two nodes were carried from Cross Stream Junction in opposite directions as long as the signal lasted. The devices were able to communicate through a rather spacious (2x3 m) tunnel + with no line of sight over at least four sharp turns. The total walking distance covered was ~40 m. + +![Cross Stream Junction with no relay](wet_sink_cross1.svg "Cross Stream Junction with no relay") + +4. Additional relay node was added right at the Cross Stream Junction. Mobile nodes were again carried in opposite directions. The total walking distance covered was ~70 m across the same sharp bends + plus some smaller tunnel irregularities. + +![Cross Stream Junction with a relay](wet_sink_cross2.svg "Cross Stream Junction with a relay") + +The testing was intentionally performed in confined parts of the cave to check the worst case scenario first and the above distances indicate performance of the system under such conditions. +In spacious caves, both horizontal and vertical, there's no reason why the links couldn't reach the usual surface line-of-sight range, that is up to 200 m in case of the 2 dBi antennas. + +The above drawings are based on the 2004 survey drawn by Paul W. Taylor, simplified for readability. + ## Footnotes [^1]: M. D. Bedford; G. A. Kennedy [Modeling Microwave Propagation in Natural Caves Passages](https://ieeexplore.ieee.org/abstract/document/6933914/), IEEE Transactions on Antennas and Propagation, 2014 diff --git a/wet_sink_crawl.svg b/wet_sink_crawl.svg new file mode 100644 index 0000000..7baa5a5 --- /dev/null +++ b/wet_sink_crawl.svg @@ -0,0 +1,356 @@ + + + + + + + + arrow-down + + + + radio-tower + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + 0 + 10 + 20 + 30 + 40 + 50 + 60 + 70 + + + Cross Stream Junction + Wet Sink cave, Gloucestershire, England + Only initial series shown for brevityinkins + + + + + + diff --git a/wet_sink_cross1.svg b/wet_sink_cross1.svg new file mode 100644 index 0000000..135a673 --- /dev/null +++ b/wet_sink_cross1.svg @@ -0,0 +1,349 @@ + + + + + + + + arrow-down + + + + radio-tower + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + 0 + 10 + 20 + 30 + 40 + 50 + 60 + 70 + + + Cross Stream Junction + Wet Sink cave, Gloucestershire, England + Only initial series shown for brevityinkins + + + + + diff --git a/wet_sink_cross2.svg b/wet_sink_cross2.svg new file mode 100644 index 0000000..f69b9cd --- /dev/null +++ b/wet_sink_cross2.svg @@ -0,0 +1,356 @@ + + + + + + + + arrow-down + + + + radio-tower + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + 0 + 10 + 20 + 30 + 40 + 50 + 60 + 70 + + + Cross Stream Junction + Wet Sink cave, Gloucestershire, England + Only initial series shown for brevity + + + + + + diff --git a/wet_sink_evel1.svg b/wet_sink_evel1.svg new file mode 100644 index 0000000..8415e04 --- /dev/null +++ b/wet_sink_evel1.svg @@ -0,0 +1,317 @@ + + + + + + + + arrow-down + + + + radio-tower + + + + + + + + + + + + + + + + 0 + 10 + 20 + 30 + 40 + 50 + 60 + 70 + + Wet Sink cave, Gloucestershire, England + Entrance series elevation only + + + MOUSE AVEN + CHOKE + BALCONY PITCH + PEN POT PITCH + + + + + + + +