Measuring height above sea level / ground with accuracy

[moogradod]

I am looking for a possibility to measure the height of the current location with a mobile device and high accuracy (my idea is something around 1 m resolution). I intend to use it to determine the possibility of water influx when deciding on the location of a new house - together with a topographic map. Third source for that would be interviewing neighbors - but I am not really convinced that I could trust them.

 

Has anybody ever done that and if yes are there any recommandations ? There seem to be two systems, based on either GPS triangulation or hyperbaric measurement. I doubt that any mobile phone app could satisfy my requirement of accuracy. The solution does not have to be dirt cheap - its part of the budget for the house). I have searched special devices like Garmin but they do not give proper indication of accuracy either. GPS should acutally be more accurate (maybe both systems would require calibration) but since I do not have access to military equipment this is maybe nothing than wishful thinking.

 

Thanks for any replies or comments.

[Kwasaki]

I found our village location is 2M above sea level on a internet map from memory.

 

For finding house location has nothing to do with sea water level you need to know does the location flood badly from flooding  rain in the future house area.

 

When we knocked down our old house which could be flooded up to knee level in heavy rains we land filled level with the road and then land filled another 2M high for the house foundation height. 

 

 

[degrub]

Maybe the government organization responsible for flood water management already has maps for your area ? 
 

Satellite lidar or gps would get you close, but they have to be referenced to a known point with a known elevation.

 

The location could flood from local rainfall, floodwater runoff from upstream , or sea tides or all of the above. Been there, done that. So, knowing the elevation relative to the peak tides with any future proofing may not be enough. 

[kokesaat]

Some food for thought:

One problem in Thailand....maybe elsewhere......is that your neighbor might very well dump trucks of dirt on his land to avoid water problems.....after you have built.  Another problem....you build a house and compensate for water runoff.  But the city/village builds/improves a road by raising the height of a road, thus altering the course of runoff.  Another problem:  In Udon, for instance, there was city-wide flooding in the year 2000.  While the city has taken some steps to reduce the possibility of same flooding, hundreds of new buildings/subdivisions/roads have been built since.  If we have the same 13" of rain in 6 hours, there will most certainly be severe flooding.....but likely in different areas than back in 2000.

 

You can get a pretty good idea of the lay of the land from google earth.....avoid the bottom of soup bowls (like the center of Udon) for starters.

If you're dealing with a flat piece of land (like a rice field), I'd add an extra meter of dirt to whatever you feel is enough.   I can show you lots of rice fields where an extra meter of dirt would keep you dry.....except for that 20-year storm that might be just around the corner.

I'd stay away from any klongs/rivers/drainage areas.

Build your house so it's a meter or so above ground.  Our 1700sf cement house sits on about 24 cement pillars......the space under the house gives us a place to store misc things and keeps us dry even in the wettest of years.

Good luck!

[KhunLA]

As stated, it's going to depend on immediate location, and water drainage of, in that area.  

 

1 of 3 builds, we had to add dirt.  Simply to make it level, what house actually sat on, as the rest (1 rai) pitched downward, and wasn't an issue of flooding or standing water. during heavy rain.

 

Other 2 building lots were high & dry, and nothing around higher, backing up to hills or waterways nearby.  Some waterways, don't exist during dry season, so sat photos may help identify them.

 

Google Earth will give a ballpark idea of sea level, though unless at surfside, not that helpful, unless surrounding area is much higher than you.

[moogradod]

33 minutes ago, Kwasaki said:

I found our village location is 2M above sea level on a internet map from memory.

 

For finding house location has nothing to do with sea water level you need to know does the location flood badly from flooding  rain in the future house area.

 

When we knocked down our old house which could be flooded up to knee level in heavy rains we land filled level with the road and then land filled another 2M high for the house foundation height. 

 

 

Thank you all for all the interesting comments. Actually the idea is to buy a house already finished and ready to move in. Just dont want to be surprized that we suddenly stay in the water as so many have been even lately. And there is more to come. We have gone through building one house (at least that is what they called this construction) in the country once. I would not have the nerve to go through that again and I fear as well that price-wise it could run out of control.

Edited September 8, 2022 by moogradod

[degrub]

Maybe that is Mean Sea Level ?

2nd floor and a bicycle ????

[phetphet]

There are app s for the iphone for that. Not sure how accurate they are though.

[moogradod]

1 minute ago, degrub said:

Maybe that is Mean Sea Level ?

2nd floor and a bicycle ????

Mean in any case. I would actually dream of owning a boat - but under different circumstances ????

[Kwasaki]

8 minutes ago, moogradod said:

Thank you all for all the interesting comments. Actually the idea is to buy a house already finished and ready to move in. Just dont want to be surprized that we suddenly stay in the water as so many have been even lately. And there is more to come. We have gone through building one house (at least that is what they called this construction) in the country once. I would not have the nerve to go through that again and I fear as well that price-wise it could run out of control.

If the houses you are looking at are already built I would of thought asking local people about flooding would the best and look at other houses in the area. 

If it's a new estate of several houses built in an area again I would think today's drainage tectnic would be already in place. 

[moogradod]

1 minute ago, phetphet said:

There are app s for the iphone for that. Not sure how accurate they are though.

I have had a look at that. Never seen any apps that gather so much information from your phone - and I am severely allergic to share personal data. I would not use them even if they were accurate (which they are not I suppose anyway - a dedicated GPS such as the better Garmin models might well be above THB 20K). And this is the price I have seen on websites abroad - might be a multiple in Thailand.

[moogradod]

2 minutes ago, Kwasaki said:

..................

If it's a new estate of several houses built in an area again I would think today's drainage tectnic would be already in place. 

We stay near Pattaya ..... Drainage technique would be nice, though - but I am not so sure if this would be an item to save building cost on.

[Muhendis]

If you download Google Earth, that will tell you the mean height above sea level at whatever location you zoom into.

I have it on my PC. I don't know if there is an app for this for a mobile "phone.

Edited September 8, 2022 by Muhendis

[Brock]

there is an app for Android, called GPS test it can show you current altitude ( according to the satellites _) above sea level. Dont be surprised if it shows a minus value, as a lot of coastal areas a pretty low. Looking at google earth will give you a really good idea , in fact if you go to street view of your location it will give you a rough indication of altitude at eye level.. For my place its 5 meters.

If you are worried about data tracking, you can uninstall the app when done with it.

[Cake Monster]

Just download a mobile App called " GPS Tools "

It has Topography, and Altimeter, Various Sensors Etc Etc Etc, as well as many other functions such as Compass, Speed, Map Tools, Weather, 

I dont know if it will be accurate enough for you, but Hey ! its free, so give it a try.

[VocalNeal]

Some hand held GPS devices have a barometric altimeter. But you have to zero them at sea level to be really accurate.

[AsianAtHeart]

MY OPINIONS:

 

1) Google Earth is not terribly accurate.  It suffers some of the same flaws as the GPS units do with respect to elevation.  The problem is that the triangulation with satellites yields more unstable results as those satellites near the horizon--and it is those nearest the horizon which should, in theory, provide the best depth perception.  A satellite that is directly overhead cannot easily read the surface terrain.

 

2) Neighbors' reports are unreliable.  Before we bought some land, we were led to believe flooding would be no issue.  After the purchase, the tune changed.  Sure enough, flooding was an issue, and we ended up trucking in tons of earth fill.  Rather disappointing on that count.

 

3) Because barometric pressure is unstable, it may require having close calculations, but, in theory, with a barometer to give the exact barometric pressure, and a very good thermometer to measure the temperature of water boiling, in addition to calculations of atmospheric temperature and humidity, an elevation can be calculated.  I do not know exactly how accurate this method is, but I know, on the basis of the boiling water, that Dr. David Livingston was able to quite accurately map parts of Africa many years ago.  I believe that, given accurate data and accounting for all of the complicating variables, it is possible to be quite accurate with the altitude. 

 

Here are some links to get started with the information, though none of these seems to be a complete and perfect fit to your needs by themselves:

 

https://www.engineeringtoolbox.com/boiling-points-water-altitude-d_1344.html

 

https://www.omnicalculator.com/chemistry/boiling-point-altitude

 

https://waterinformer.com/boiling-temperature-of-water-at-different-altitudes-across-the-globe/

 

To be able to get precise enough for this to work, though, you'll have to have a very precise thermometer.  Fifty feet in elevation will change the boiling temperature of water by only about 0.1 degrees.  So if you want 5-foot accuracy, you'll need a digital thermometer that gives temperatures in hundredths of a degree -- in addition to having accurate data and equations for the calculations which properly account for other factors (starting with pure, distilled water, to help eliminate inaccuracies, for example).

 

 

[moogradod]

5 minutes ago, AsianAtHeart said:

MY OPINIONS:

 

1) Google Earth is not terribly accurate....... 

 

2) Neighbors' reports are unreliable.......... 

 

3) Because barometric pressure is unstable, it may require having close calculations, but, in theory,

..........................

...................

So if you want 5-foot accuracy, you'll need a digital thermometer that gives temperatures in hundredths of a degree

Thank you for your extensive elaboration about the subject !

 

Unfortunately you confirm most of my worries. As for the barometric method: I do not intend to write a dissertation about it - and the fact that I would need a thermometer with a precision down to a hundredth of a degree.....better forget.

 

You mention Dr. Livingston. You mean THAT Dr. Livingston "I presume" ???? If so than that is indeed some time ago. ???? Livingston died in 1873. Interesting that technonolgy has not evolved to such a degree since then that what used to be a complicated procedure cannot be obtained in a $10 handheld device nowadays.

[moogradod]

56 minutes ago, VocalNeal said:

Some hand held GPS devices have a barometric altimeter. But you have to zero them at sea level to be really accurate.

If this were all that was to it - done in a jiffy. Our condo house is located right at the beach. All I needed to do is to walk down to the lobby

[AsianAtHeart]

1 minute ago, moogradod said:

If this were all that was to it - done in a jiffy. Our condo house is located right at the beach. All I needed to do is to walk down to the lobby

Well, why didn't you say so?

 

If you are within 300 feet of the water (and if not you could just do this in steps, by marking points along the way and doing simple math to compute the accumulated drop), you could buy 100 meters of transparent water hose/tubing (might cost around $40? -- I don't remember), and carefully fill it with water whilst elevating both ends such that the water does not escape.  Try not to allow air bubbles in the hose (this is tricky).  The water in the hose can act as a level.  It should be the exact same height at each end, once the hose is stabilized so that wave motions have petered out. 

 

With the water level matching your front doorstep, take a tape measure to the other end of the hose and measure down from the height of the water in the hose to the height of the sea surface.  That's how many feet of elevation you would have.

 

Now your chief difficulty will be in determining the tide elevation at time of measurement.  There are tide tables online that should help with this.

[moogradod]

3 hours ago, Muhendis said:

If you download Google Earth, that will tell you the mean height above sea level at whatever location you zoom into.

I have it on my PC. I don't know if there is an app for this for a mobile "phone.

Thanks. I have it on all of my PCs, too. In fact I hate mobile phones but you cannot live without them the more time passes. Helpful at least if my missus is on a shopping crusade and wants to show me something before buying. Nice feature this video call.

[moogradod]

6 minutes ago, AsianAtHeart said:

........

 

Now your chief difficulty will be in determining the tide elevation at time of measurement.  There are tide tables online that should help with this.

You would not believe it but I have even that ! I was once interested about the tides at our location and I found a table. Given your level of proposed accuracy then there are of course the waves to be accunted for. The sea is not flat but in constant motion......

[Pooreye]

To be safer you must look around carefully... like walking around inside village and looking for traces of 2011 floding in Pathum Thani.

The pictured one, everything looked good and never flooded before. Never inundated. Guaranteed! 
Oh by the way can I look inside the garage please?

Eeeeh okay....

[GreasyFingers]

Local flooding has nothing to do with height above sea level so even if you knew it, it would be of no use to you. If you were in a civilised country there would be local benchmarks that a surveyor could relate your land to. There shoul be a surveying firm somewhere in your area that can help you.

Even though the Thai land Office use a coordinated system (GPS) for boundaries i do not know if they record land heights as well. You could talk to their surveyor at the Land Office.

[GreasyFingers]

5 minutes ago, moogradod said:

You would not believe it but I have even that ! I was once interested about the tides at our location and I found a table. Given your level of proposed accuracy then there are of course the waves to be accunted for. The sea is not flat but in constant motion......

Waves are determined by wind. Strong winds, even 100km from you, can cause a much larger setup above the tide.

[moogradod]

16 minutes ago, GreasyFingers said:

Local flooding has nothing to do with height above sea level so even if you knew it, it would be of no use to you. If you were in a civilised country there would be local benchmarks that a surveyor could relate your land to. There shoul be a surveying firm somewhere in your area that can help you.

Even though the Thai land Office use a coordinated system (GPS) for boundaries i do not know if they record land heights as well. You could talk to their surveyor at the Land Office.

The height might be useful if you combine it with a topographic map. But your idea to seek help from the local Land Office is a good one. I just had a look at the copy of the chanote of the land my wife posesses. Indications on the drawing are only some strange numbers near to the "pillars" that show the boundaries, and these were not coordinates, either. Not to speak about elevation.

Edited September 8, 2022 by moogradod

[moogradod]

15 minutes ago, Pooreye said:

To be safer you must look around carefully... like walking around inside village and looking for traces of 2011 floding in Pathum Thani.

The pictured one, everything looked good and never flooded before. Never inundated. Guaranteed! 
Oh by the way can I look inside the garage please?

Eeeeh okay....

Excellent ! Thanks for this easy but very practical advice.

[GreasyFingers]

3 minutes ago, moogradod said:

The height might be useful if you combine it with a topographic map. But your idea to seek help from the local Land Office is a good one. I just had a look at the copy of the chanote of the land my wife posessses. Indications on the drawing are only some strang numbers near to the "pillars" that show the boundaries, and these were not coordinates, either. Not to speak about elevation.

The Land Office may be reluctant to give you the information, even the coordinates of your land. It is freely available in other countries as it is on public record.

[moogradod]

I would like to express my gratitude to everyone - without exeption - who has posted here in response. You all made my day. It is increasingly often that when asking for help here on the forum you get some rather disturbing comments instead of answers with a compassionate attitude - or even no answer at all. This was not the case here.

 

Thank you all again and I wish everybody a nice evening.

[blackcab]

If you use Google Earth, understand that elevation data refers to the Local Mean Sea Level. That's a really crucial thing to understand if you are researching flood risk.

 

For example, if you check google earth for the height of the sea that is next to Pattaya beach, the beach itself has an elevation of 2-6 meters, even though it is at what most people would perceive to be sea level.