newtothis
Well-Known Member
Even ugly budgies too. Bloody autocorrupt.
How to work out my height above sea level?
- Thread starter MissFitz
- Start date
Stemar
Well-Known Member
OTOH, there may be advantages to using the neighbour's pet, especially if it's a yappy dog...
laika
Well-Known Member
It depends *where* on the seafront. If, say, marine parade you might be rather underestimating. You've got sea level to madeira drive , madeira drive to marine parade, marine parade to second floor. Those whose suggestions require knowledge of horizontal distance to calculate height are possibly unfamiliar with the beach, as calculating said horizontal distance to the water's edge would be a challenge in itself. I like lw395's suggestion best. GPS heights are supposed to be unreliable but I would doubtless cross-reference a few height calculations from noon sights with what my phone told me corrected by height of tide.
capnsensible
Well-Known Member
Wait until it goes to sleep.
AntarcticPilot
Well-Known Member
GPS heights are slightly less accurate than the horizontal accuracy, so given present technology I'd expect a vertical accuracy of around 5m; perhaps better. However, the problem is that GPS height isn't measured with respect to sea level, it is measured with respect to an artificial surface that is a best fit to sea level, but which differs from it by up to about 100m. In the UK, the difference is in the region of 10-20 metres.
Therefore, to use GPS to get height above sea level, the technique would be to take several height readings at a known height above sea level (e.g. at the sea shore), average them and then subtract this value from the average of several readings at the observation position.
If you can record an hour or so's height measurements at each location, the resulting averages should be significantly more accurate than single readings. Of course, if you have access to survey grade kit, you can get elevations good to a few cm, but would still need to take the difference between a point of known height wrt sea level and the observation point.
MissFitz
Well-Known Member
Lots of excellent and interesting suggestions, thank you. I now know what ordnance datum is!
I’m on Brighton and Hove borders, so right down at seafront level, but the beach shelves so steeply here that you can’t even see the second floor from the high water mark. So I think the easiest way is probably to take sights and work back to altitude. Sadly the sun is too high now for noon sights from the flat (no balcony....) but I can presumably use a series of other sun sights and average. Good practice too
I’m on Brighton and Hove borders, so right down at seafront level, but the beach shelves so steeply here that you can’t even see the second floor from the high water mark. So I think the easiest way is probably to take sights and work back to altitude. Sadly the sun is too high now for noon sights from the flat (no balcony....) but I can presumably use a series of other sun sights and average. Good practice too
dutyhog
Well-Known Member
I did this many years ago when ill in bed and bored while recovering. The bed overlooked the Clyde directly south and we lived hundreds of feet up a hill. Get the noon sextant angle between the sun and it’s reflection - off the calm sea in your case, it was the river for me. Halve the angle to get the sight and use tables or geometry to calculate your height. It was amazingly accurate according to the OS contours.
Frank Holden
Well-Known Member
You need a simple surveyor's level .. something like this ... vintage Surveyors Sight Level ... QUIKSITE | eBay
..along with a
Job done...
In fact ... if it is all up hill you don't even need the stick... just line up on friend's shoes ... each 'step = your height of eye = 5 foot 6 inch or whatever...
zoidberg
Well-Known Member
I'm wondering if 'capnsensible' - or another dolphin - can suggest a way of measuring depth below sea level, while allowing for variations in salinity and temperature.....
blackbeard
Well-Known Member
Reminded of many happy lunch breaks using an ashtray filled with water to give a level reflecting surface, as suggested above; independent of height, halve the angle, apply corrections for sextant and atmospheric refraction.
As an encore, you can use the real horizon and then back-calculate to give height of apartment above sea level. For a bit more practice, you can work out height of tide at the time (approximately).
As an encore, you can use the real horizon and then back-calculate to give height of apartment above sea level. For a bit more practice, you can work out height of tide at the time (approximately).
AntarcticPilot
Well-Known Member
The professionals do it by taking regular CTD casts to measure the salinity and temperature throughout the water column. Not practical for us!
capnsensible
Well-Known Member
Bit of line with a small lump of lead on the end. I believe its still called a 'lead line'. One can use this to measure depth in seconds then take dinghy to bar and read this thread on ipad/tablet thinghy and spend ages reading about all the hard ways of solving a basic problem.
zoidberg
Well-Known Member
I'm wondering if 'capnsensible' - or another dolphin - can suggest a way of measuring depth below sea level, while allowing for variations in salinity and temperature.....
Bit of line with a small lump of lead on the end. I believe its still called a 'lead line'. One can use this to measure depth in seconds then take dinghy to bar and read this thread on ipad/tablet thinghy and spend ages reading about all the hard ways of solving a basic problem.
I didn't explain that too well.
What I had in mind was measuring UP from the hapless observer......
Iliade
Well-Known Member
That's easy! Fender on a string.
Frank Holden
Well-Known Member
Far too simple.... walk to water's edge with sextant..... measure sextant altitude of balcony using artificial horizon.... lift distance from observation point to front of building from Google Earth..... use the reverse of the normal 'distance off by vertical sextant angle' ie rather than using angle and height to find distance off use distance off and angle to find height of object....
Lockdown? what lockdown?????
Beneteau381
Well-Known Member
Bit of Fred drift but encouraged by talk of lead lines. In Holyhead Marina before setting off darn scarf I set the depth guage by dropping a lead line off the sugar scoop and measuring from the sea floor to the tip of the sugar scoop which as near as damn it is water level. I then set the depth at that on the guage A few years later leaving Bruces yard and going down the channel just after hi Water I was Carefully watching the depth as we followed him out. The depth dropped and dropped but we kept on going, we draw 1.6 and it got down to 1.3 at one point! I was twitching but we kept going. Afterwards talking to Bruce, he said, we have dredged the channel, minimum of two meters at all times. I suspect that muddy waters was the cause!For many years, the sky has been my ceiling.
Actually I was thinking of Brighton, sea level to road, road to second floor. Bit OTT? Lead line!
DJE
Well-Known Member
This should give you a good idea of street levels (in feet above mean sea level).
Old OS map
Then add about 10 feet per storey or count the stairs.
Old OS map
Then add about 10 feet per storey or count the stairs.