Elevation data

[John316]

Hello,

I am new to Irricad, so please stay with me during my learning curve. I attended the Irricad foundation/training course, which I found very beneficial.

My question is, where can I get data information? Google Earth has the elevation data, but to date there is no way to access that data. I know the USGS has maps, but the contour increments are to large (50 ft). Is there anywhere I can get the contour information in five foot increments? I don't mind buying software, but where can I find the information?

Thanks in advance.

Sincerely,

John

[Dan Crosby]

Hi John,

There are numerous sources of elevation data, if you are prepared to pay - Google may be your friend here..

One such source is:

http://www.intermap.com/

Note when looking for data, that contour information isn't always available, however neither is it necessary for Irricad - spot heights work too. I will mention that v11 of Irricad will be able to generate contours from spot heights, and will have much improve handling for elevation calculations.

Regards - and Happy Holidays! -

Dan

[Hutch]

Hi John

Publicly available elevation data is often not accurate enough for irrigation design purposes, particularly for drip irrigation design where pressures are low and errors in elevation of even a few feet can be disastrous.

We are currently working on some things that may help. I'll keep you posted.

Hutch

[John316]

Gentlemen,

Thank you for the replies.

Dan, your information was very interesting. First off, rest assured I have spent a significant amount of time using google as I try to find the data I am searching for. I am aware of a place that provides contours in five foot increments. The problem arises from the fact that I do not know who that company is.

Hutch, thank you for the reply. I understand that the publicly available information isn't ideal. However, if I am able to find a place that I can get elevation data in five foot, or less increments, then that would be a huge help.

Thanks again for your help.

John

[aquacg]

Hi, can anyone explain the process to download a 'field' form intermap.com with accurate elevation data to be imported into Irricad? The site says the that 40% of the data is < 1m accurate, 40% is 1-3m accurate and 20% is >1m accurate. Do we know what it is when it is downloaded? Can I download accurate enough elevation data for drip design? If not, are there any other sites better for this that allows you to define an AOI and download and pay for only that data? Thanks.

Corby

[Dan Crosby]

Hi Corby,

From a quick look at the website it would appear that you have to take a year-long subscription to data at a US county level - and it seems to be quite expensive (that's the Premium, and presumably most accurate data).

For the basic data you can draw an AOI on top of the map on the purchase page and get a quote for the data in that area. See the 'Demo' link on the Intermap purchase page (top right) to see how this is done.

It isn't obvious what format the downloaded data comes in, nor the accuracy of it. However, you must remember that it is the relative accuracy that is important, not the absolute accuracy. It doesn't matter if the height of your whole field is 300 feet out, if one end of the field is accurate relative to the other. You'd have to ask Intermap about these things.

Dan

[aquacg]

Thank you for your reply. As I am new to irricad also, I am looking for the cheapest and most accurate source of elevation data for designs. It looks like there is a $480 minumum for single AOI downloads from this site. What is your opinon of the best and cheapest source. Also, what format is best for irricad to upload point elevations or contours. Do I need contours or are point elevations enough to allow irricad to generate the contours? Thanks.

[jovivier]

Corby,

Maybe someone in the US can answer your specific questions regarding elevation data for the US.

To be able to import elevation data in to IRRICAD the file needs to be in DXF, SHP, or CSV (*.csv, *.txt, *.xyz) format.
You can create contours from point elevations using Tools|Calculate Contours.

[John316]

Corby,

I think your best bet is to get RTK gps of the field. You know that will be accurate. Otherwise, with Intermap select your AOI to fully utilize the $400 minimum.

HTH