How to calculate lot size

[pomchop]

Ok for all you math gurus here is a pic of the actual lot...not sure if you can calculate the angles you guys are talking about from this or not....but this is all the info I have....the measurements are all shown in feet as the lot is in the USA. I'm ok with the previous 758 sm but if anyone wants to keep calculating go for it.

Pomchop,

758 sqm is area if it's cyclic quadrilateral shape. If it's not, you need to know at least one of the diagonal length or angel of any one of the corners. Looking at your picture it may not be cyclic quadrilateral meaning all four vertices must lie in a circle. Best way to be sure is measure the distance of any two points.

Thanks for all your help. I'm afraid all of this is over my head but I do think that your 758 seems about right when I compare it to lots that I know to be about 1000 square meters.

Amazing how complicated it seems to be...I would never have dreamed of all the formulas and calculations that it seems to require. Maybe I should have been paying a bit more attention to the teacher in school and a little less attention to the cute girls.

[Crossy]

This tool works quite well http://acme.com/planimeter/

Find the plot on Google maps and trace its outline, shows the area in m², hectares, km², ft², acres and miles²

Another one here http://www.daftlogic.com/projects-google-maps-area-calculator-tool.htm but it doesn't zoom quite so close so not as good for small plots.

And yet another http://www.freemaptools.com/area-calculator.htm

No idea if these all use the same engine, but they give results pretty close to one another (and agree with our chanote).

[Paul888]

Best thread of the year so far for me. Very interesting question and some great answers. Some real expertise here.

Looking forward to explaining to my kids why learning all those maths formulas isn't a waste of time

[villagefarang]

This tool works quite well http://acme.com/planimeter/

Find the plot on Google maps and trace its outline, shows the area in m², hectares, km², ft², acres and miles²

Another one here http://www.daftlogic.com/projects-google-maps-area-calculator-tool.htm but it doesn't zoom quite so close so not as good for small plots.

And yet another http://www.freemaptools.com/area-calculator.htm

No idea if these all use the same engine, but they give results pretty close to one another (and agree with our chanote).

Very nice answer Crossy, and for me it reiterates why it is unnecessary, in this modern age, to learn math formulas. With decent search skills, one can find answers to almost anything on the internet.

Why clutter ones grey matter with seldom used formulas when there is so much to be seen and experienced in our short time on this planet? Just offering up a non-engineer’s perspective.

[Paul888]

This tool works quite well http://acme.com/planimeter/

Find the plot on Google maps and trace its outline, shows the area in m², hectares, km², ft², acres and miles²

Another one here http://www.daftlogic.com/projects-google-maps-area-calculator-tool.htm but it doesn't zoom quite so close so not as good for small plots.

And yet another http://www.freemaptools.com/area-calculator.htm

No idea if these all use the same engine, but they give results pretty close to one another (and agree with our chanote).

Very nice answer Crossy, and for me it reiterates why it is unnecessary, in this modern age, to learn math formulas. With decent search skills, one can find answers to almost anything on the internet.

Why clutter ones grey matter with seldom used formulas when there is so much to be seen and experienced in our short time on this planet? Just offering up a non-engineer’s perspective.

There is nothing wrong with using tools created by others to find your answers quicker, but considering that most of the information on the internet is crap, it is wise to have at least a passing knowledge of how to check things yourself. As a parent who cares how his children make their way in this world after he is gone, I value the development of an inquistive and problem solving mind over the ability to sit, click and believe whatever comes across the screen.

[villagefarang]

I suppose it is anyone’s guess, what skills may end up being most productive and applicable in the future. Hard science is definitely one way to go. My right brain bias no doubt influences how I look at things.

[Sophon]

Ok for all you math gurus here is a pic of the actual lot...not sure if you can calculate the angles you guys are talking about from this or not....but this is all the info I have....the measurements are all shown in feet as the lot is in the USA. I'm ok with the previous 758 sm but if anyone wants to keep calculating go for it.

OK, measuring the diagonal from the right side corner on Sunset Boulevard to the opposite corner (the sharp angle corner) and comparing with the dimensions of the sides, I approximate that diagonal to be 158 feet long. Entering this information in the calculator posted by wayned the website gives this information:

Here are my calculations:

With the diagonal, the lot is divided into two triangles and I know all the lengths of the sides of these triangles, so I can use Heron's formula to find the area of each triangle:

SABC = (50 + 139 + 158) / 2 = 173.50

AABC = SQRT( (173.50)(173.50 - 50)(173.50 - 139)(173.50 - 158) )

= 3385.0.

SACD = (158 + 100 + 94) / 2 = 176.00

AACD = SQRT( (176.00)(176.00 - 158)(176.00 - 100)(176.00 - 94) )

= 4443.3.

That makes a total for the two triangles (which is the area of your property) of:

3385.0 + 4443.3

= 7828.3 square feet

= 869.81 square yards

= 727.27 square meters

= 0.17971 acres

= 0.072727 hectares

Sophon

[Sophon]

Ok for all you math gurus here is a pic of the actual lot...not sure if you can calculate the angles you guys are talking about from this or not....but this is all the info I have....the measurements are all shown in feet as the lot is in the USA. I'm ok with the previous 758 sm but if anyone wants to keep calculating go for it.

Just to add (if anyone is still interested), the order of the four sides also makes a difference to the area so they should be stated in clockwise order.

As a simple example a convex plot with:

Angle A at 90 degrees, and

side dimensions 100m x 70.7m x 100m x 70.7m

would be a rectangle with an area of 7,070 sq.m.

While a plot with the same 90 degree angle A, and

side dimensions 100m x 70.7m x 70.7m x 100m

would effectively be a triangle with an area of 5,000 sq.m.

In your OP you stated:

50 feet x 94 x 140 x 100

But from the information on your pic the dimensions are actually 50' x 139' x 100' x 94'.

Sophon

Edited July 20, 2013 by Sophon

[pomchop]

Ok for all you math gurus here is a pic of the actual lot...not sure if you can calculate the angles you guys are talking about from this or not....but this is all the info I have....the measurements are all shown in feet as the lot is in the USA. I'm ok with the previous 758 sm but if anyone wants to keep calculating go for it.

Just to add (if anyone is still interested), the order of the four sides also makes a difference to the area so they should be stated in clockwise order.

As a simple example a convex plot with:

Angle A at 90 degrees, and

side dimensions 100m x 70.7m x 100m x 70.7m

would be a rectangle with an area of 7,070 sq.m.

While a plot with the same 90 degree angle A, and

side dimensions 100m x 70.7m x 70.7m x 100m

would effectively be a triangle with an area of 5,000 sq.m.

In your OP you stated:

50 feet x 94 x 140 x 100

But from the information on your pic the dimensions are actually 50' x 139' x 100' x 94'.

Sophon

As I said I am certainly no math guru and frankly I thought that just saying ok here are the rough dimensions that it would be some simple formula to get an approximate size...little did I realize all the calculations, angles, formulas,etc that apparently are involved. In any case I am once again amazed at all the expertise that seems to be out there in TV land....thanks to all.

[wayned]

If you use the website that I quoted earlier http://mathcentral.uregina.ca/QQ/database/QQ.09.06/s/foursidedlot.php , all you have to do is enter the length of the four sides and one angle. From your pic, the angle between the 50 and 94 line segments looks cloe to 90 degrees. Contray to what someone said earlier, it is poaaible to calculated the are knowing only the length of 4 side and one angle.

I used the angle of 90 degrees between the 50 and 94 line segments in the example that I gave you earlier, so those calculations should be correct given that the angle is 90 degrees.

[Sophon]

If you use the website that I quoted earlier http://mathcentral.uregina.ca/QQ/database/QQ.09.06/s/foursidedlot.php , all you have to do is enter the length of the four sides and one angle. From your pic, the angle between the 50 and 94 line segments looks cloe to 90 degrees. Contray to what someone said earlier, it is poaaible to calculated the are knowing only the length of 4 side and one angle.

I used the angle of 90 degrees between the 50 and 94 line segments in the example that I gave you earlier, so those calculations should be correct given that the angle is 90 degrees.

No, it's not possible to calculate an area with just the length of the sides and one angle without making some assumptions. That is why the website you quote makes the assumption that the polygon is convex, which when talking about land plots is probably correct in the majority of cases but not all.

These two polygons have the same four sides and angle A is 90 degrees in both cases, but the areas of the two figures are obviously very different because one is convex and the other concave:

When you did the calculations you assumed that the angle between the 50 and 94 feet sides is 90 degrees. While it's obvious from the pic posted later by the OP that that is not quite the case, the angle is not that far off so your estimate is quite close. As you can see in post 37 I measured the diagonal in the picture and arrived at an area of 727 sq.m. compared to your 711 sq.m.

Sophon

[Sophon]

If you use the website that I quoted earlier http://mathcentral.uregina.ca/QQ/database/QQ.09.06/s/foursidedlot.php , all you have to do is enter the length of the four sides and one angle. From your pic, the angle between the 50 and 94 line segments looks cloe to 90 degrees. Contray to what someone said earlier, it is poaaible to calculated the are knowing only the length of 4 side and one angle.

I used the angle of 90 degrees between the 50 and 94 line segments in the example that I gave you earlier, so those calculations should be correct given that the angle is 90 degrees.

No, it's not possible to calculate an area with just the length of the sides and one angle without making some assumptions. That is why the website you quote makes the assumption that the polygon is convex, which when talking about land plots is probably correct in the majority of cases but not all.

These two polygons have the same four sides and angle A is 90 degrees in both cases, but the areas of the two figures are obviously very different because one is convex and the other concave:

Convex + concave polygon.jpg

When you did the calculations you assumed that the angle between the 50 and 94 feet sides is 90 degrees. While it's obvious from the pic posted later by the OP that that is not quite the case, the angle is not that far off so your estimate is quite close. As you can see in post 37 I measured the diagonal in the picture and arrived at an area of 727 sq.m. compared to your 711 sq.m.

Sophon

I should probably qualify my above statement by saying that you cannot calculate the area with any random angle. If you happen to have the right angle (between two of the shorter sides), then the figure can by definition not be concave and there is only one possible area.

Sophon

[cooked]

Ok for all you math gurus here is a pic of the actual lot...not sure if you can calculate the angles you guys are talking about from this or not....but this is all the info I have....the measurements are all shown in feet as the lot is in the USA. I'm ok with the previous 758 sm but if anyone wants to keep calculating go for it.

This is a rectangle surrounded by triangles. That's the way I did it as a surveyor, why complicate things?

[JAG]

Just ask the wife how many Rai it is - she will know!

[pomchop]

Just ask the wife how many Rai it is - she will know!

Lot is in the USA and no wife to ask...thankfully.

[wayned]

If you use the website that I quoted earlier http://mathcentral.uregina.ca/QQ/database/QQ.09.06/s/foursidedlot.php , all you have to do is enter the length of the four sides and one angle. From your pic, the angle between the 50 and 94 line segments looks cloe to 90 degrees. Contray to what someone said earlier, it is poaaible to calculated the are knowing only the length of 4 side and one angle.

I used the angle of 90 degrees between the 50 and 94 line segments in the example that I gave you earlier, so those calculations should be correct given that the angle is 90 degrees.

No, it's not possible to calculate an area with just the length of the sides and one angle without making some assumptions. That is why the website you quote makes the assumption that the polygon is convex, which when talking about land plots is probably correct in the majority of cases but not all.

These two polygons have the same four sides and angle A is 90 degrees in both cases, but the areas of the two figures are obviously very different because one is convex and the other concave:

Convex + concave polygon.jpg

When you did the calculations you assumed that the angle between the 50 and 94 feet sides is 90 degrees. While it's obvious from the pic posted later by the OP that that is not quite the case, the angle is not that far off so your estimate is quite close. As you can see in post 37 I measured the diagonal in the picture and arrived at an area of 727 sq.m. compared to your 711 sq.m.

Sophon

I should probably qualify my above statement by saying that you cannot calculate the area with any random angle. If you happen to have the right angle (between two of the shorter sides), then the figure can by definition not be concave and there is only one possible area.

Sophon

Sorry,

You are right. If you look at the website that I quoted, it assumes that the shape is convex, not concave. In frustration, and the lack of anything else to do, I printed out the plot and measured the angles as best that I could Plugging them into the website, it comes up with 716.66 square meters. I would assume that if he uses 720 it's very close!.

[villagefarang]

I don’t know about you but I find it oddly interesting that our most active topic of late, has nothing to do with Thailand, let alone Chiang Rai.

Just a bunch of old guys sitting around debating the size, shape and angles of a piece of land in California, as well as the merits of different methods for determining the area of said piece of property.

Not sure what to make of it but I do find it intriguing.

[harrry]

I don’t know about you but I find it oddly interesting that our most active topic of late, has nothing to do with Thailand, let alone Chiang Rai.

Just a bunch of old guys sitting around debating the size, shape and angles of a piece of land in California, as well as the merits of different methods for determining the area of said piece of property.

Not sure what to make of it but I do find it intriguing.

But very useful as I have to devise a way of dividing the families Chiang Rai 's house block into 5 equal parts and it is of this shape. The link regarding the website that uses google map has proved a lifesave. Dividing the rice fields was easier because it was larger and more rectangular so I had much less calculations to do.

Enough of the old guys talk too.you cheeky young whipersnapper.

Edited July 22, 2013 by harrry

[villagefarang]

I don’t know about you but I find it oddly interesting that our most active topic of late, has nothing to do with Thailand, let alone Chiang Rai.

Just a bunch of old guys sitting around debating the size, shape and angles of a piece of land in California, as well as the merits of different methods for determining the area of said piece of property.

Not sure what to make of it but I do find it intriguing.

But very useful as I have to devise a way of dividing the families Chiang Rai 's house block into 5 equal parts and it is of this shape. The link regarding the website that uses google map has proved a lifesave. Dividing the rice fields was easier because it was larger and more rectangular so I had much less calculations to do.

Enough of the old guys talk too.you cheeky young whipersnapper.

I am an old guy too, just young at heart. Anyway, I was just making an observation.

[pomchop]

I dont know about you but I find it oddly interesting that our most active topic of late, has nothing to do with Thailand, let alone Chiang Rai.

Just a bunch of old guys sitting around debating the size, shape and angles of a piece of land in California, as well as the merits of different methods for determining the area of said piece of property.

Not sure what to make of it but I do find it intriguing.

Knowing how to figure the the size of a lot whether in USA or Thailand is useful knowledge to many. I suspect many of us would like to be able to verify what we have been told is a size here in Thailand . Every time I have asked about my lot in CR I get vague answers. Fortunately my CR lot is a more regular shape so I can hopefully measure it and figure it out more precisely. Once you get it into square meters or square feet it is fairly easy to then convert to rai.

I am impressed with the knowledge available from TV posters....it turned out to be way more complicated than I would have dreamed....thanks again..

p.s....lot is not in California...east coast.

1 sq. wah = 4 sq. m. 1 acre = 2.471 rai or 43,560 sq. ft.

1 ngan = 100 wah (or 400 sq. m.) 1 hectare = 6.25 rai or 10,000 sq. m.

1 Rai = 4 Ngan (or 1600 sq. m.)

.....