convert from HARN

I think you are correct - there seems to be no support for NAD83(HARN) in the Trimble Coordinate System Database.

If were to be needing those numbers in realtime, I would probably survey with NAD(83) SPC and a geoid model. That should get you close. I would set the base over a known point or use a Site calibration to adjust.

But for that you will need at least 2 and preferably more, control points with given numbers, which it sounds like you do not have.

Are there any NGS marks nearby that have HARN numbers?

If they can not provide that, I would run, not walk, away from the job...

Just my nzd$0.02

HARN, which stands for High Accuracy Regional Network was a current thing in the late '90s. It is seriously obsolete now. In my area it differs from the current flavor, NAD83(2011), by a half foot or so. Is that a significant difference for this project?

Frankly, I would likely refuse to engage in the sort of situation you describe. I don't mind staking from DTMs and such, but I do mind staking things that have not been engineered in any proper way. Too much chance of things going down the drain and carrying me with it. I have the fancy toys and know how to use them.

>"I think I understand that HARN is “very close” to SPC, so I thought I’d shoot it in SPC and convert in post."

HARN is an old datum. SPC is a projection. You need to specify both.

Perhaps your state has a latest SPC defined with a specified datum so your statement could make sense, but it is ambiguous at best.

Just like NAD83 (2011), HARN is a realization of NAD1983. It was a first attempt at a GPS derived control network and was mostly derived by FBN and CBN stations co-observed by NGS and local surveyors. Different areas have a different realization data for HARN. Oregon & Washington were among the first with observations made beginning in 1989 and realization better known as NAD83(91). Each region's HARN has a different realization date depending on when it was surveyed with no real tie between 'HARNs'. It took close to a decade for the HARN to be established nationwide. NGS the decided it would be best if all the observations were readjusted as a nationwide realization and thus NAD83(98) was born. There has been a lot of movement around these parts since 1989 which by itself causes issues. There is no simple method to get form a so called HARN to a current realization without readjusting or performing some local transformation.

The problem with most CAD and GIS packages is that they seem to think that there are simple transformation from realization to realization. They like to give you a large selection of flavors of any given coordinate system based on NAD 1983 (NAD83(86), NAD83, NAD83 HARN, NAD83(NRS2007)...). The HARN variety is usually at the top of the list and gets pick when someone is looking them over. Chances are your project may not really be HARN. Personally, I like to specify just plain jane NAD83 when choosing coordinate systems in CAD.

On a side note, if the engineer can not provide any control or meta data for the you to check against, I would refuse to lay it out or a least find a way to cover your ass.

HARN is/was GPS derived control of various NAD83 epochs (recalculated following NAD83 shifts). It is still valuable because it consists of physical monuments that can be occupied, normally with very high vertical accuracy values since they often were placed on first order bench marks. What you really need to "convert" is to know which epoch of HARN is being referenced. Then convert from NAD83(93) to NAD83(2010). Or whatever HARN value was actually applied to the monument to control the project. I kinda figure this company can't answer that question. But if they used GPS to control the design, they have to provide control, even if that control monument is the nearby HARN monument. Otherwise, you're only guessing.

There can't be a HARN to SPC conversion. HARN is SPC and if you look at a datasheet it will have various epochs of NAD83. So there is no HARN to NAD83(2011) conversion. My last check a few weeks ago to a HARN monument using CORS values was .02' horizontally (RTK check so not highly accurate) and of course the HARN point vertically is way better than CORS but CORS/OPUS was within .05' vertically which I figured was outstanding.

Mahalo (thank you) to all of you. As usual, I come away from this with not just more bits of new info I can tuck away, but as importantly, how you think about stuff ("I'd walk away" lol). This job at this point is "just for a basin" and I'd set a reference elevation off a relatively flat spot on the road in their topo so the datum is basically mute now. I've heard the engineer is 1000's of miles away, fairly young, has no eyes on the ground here and has taken on a job that may be bigger than he is (or may give him some good lessons to grow from). IMO the basin is poorly designed for the particular site and he will certainly see the results of that within a few good rainy years. I've talked with the contractor about it, but have no way (or need) to contact the engineer about it. So I think I've covered my arse and the contractor has info he can use to build the basin as designed, good or bad. Thanks again.

I hope this will help - a bit long but good history. First as john-putnam noted the HARNs were just different realizations of the original adjustment which came out in 1986. It wasn't until NGS had completed the first HARN (TN) in 1989 that we were faced with how to express the new coordinate values with respect to the original values that had just come out three years before. Good, bad or indifferent we chose to label the coordinates as NAD 83 followed by the year the HARN was adjusted. Since they were done between 1989 - 1997 various states have different dates for their coordinates. Second - State Plane Coordinates are not a specific realization unto themselves. They are mathematically related directly to the foundational latitude and longitudes that define any specific datum and/or datum realization, the same is true for UTM coordinates.

What's commonly referenced as HARN (High Accuracy Reference Network) were originally called HPGN (High Precision GPS Network) when NGS started this effort in 1989 in Tennessee, the program was given the name change in 1992. They were observed typically state-by-state although a few were combinations like Delaware & Maryland, Oregon & Washington. Each project received it's own date of completion such as Maryland - NAD 83 (1991), Oregon - (1992), the last being Indiana - NAD 83 (1997). By mid-1995 two things had happened. NGS had developed very good guidelines to determine GPS-derived NAVD 88 orthometric heights which required very accurate ellipsoid heights and the proliferation of CORS had taken off. Until around 1994 NGS really didn't make any serious effort to worry about the ellipsoid heights and later as CORS were introduced some states such as OR-WA had found positional differences in excess of 5cm when comparing HARNs with local CORS. With the completion of the last HARN the field units did not shop but went into upgrade mode do one more survey this time called the Federal and Cooperative Base Networks (FBN/CBN). Under new guidelines the surveys were designed to ensure that the corresponding ellipsoid heights would be no worse than 2 cm (95% confidence). The agency finished the last of those in 2004. That led to the first national adjustment of some 60k passive GPS control that NGS had collected which became NAD 83 (2007). Four years later following the second Multiyear CORS Soultion (MCS) all the passive network now more than 80K stations were adjusted to fit that frame giving us the current NAD 83 (2011) Epoch 2010.00 - A small misnomer john-putnam "NGS decided it would be best if all the observations were readjusted as a nationwide realization and thus NAD83(98) was born." I suspect you're in the OR/WA area in which case NAD 83 (98) is the realization of the FBN/CBN surveys I noted above. NGS has developed transformation grids that will go between all of the HARN, FBN/CBN and national adjustments, you just need to know which realizations you're dealing with. They are all include in the NCAT (National Coordinate Conversion and Transformation Tool) -- https://geodesy.noaa.gov/NCAT/. If you're not sure which ones your state has open NCAT and look for "Don't see a reference frame in the list?Click here to learn more" near the bottom center of the page. Click on that and it will give you which realizations apply to all states & territories. I hope this tale is helpful.

"This job at this point is “just for a basin”

I don't even know what that statement means but there is no way that I am touching that job without all of the information that I need to feel absolutely confident in the H & V control. If you can't give me the information that I need, you have two options, pay me to redo the outbounds and topo and adjust your design to my data or I walk away.

There is no way for you to determine whether your layout is right without the supporting design control. When you start talking weirs and storm piping, sometimes close enough doesn't work when the train derails. Usually "just a basin" turns into a whole different animal. Don't walk, run!!

"I hope this will help – a bit long but good history."

Yes. Others alluded to this, but this is comprehensively clear and helpful. I wasn't completely knowledgeable as to how HARN related to the datums and coordinate systems I'm used to or even what HARN really is, even after an hour or more seeking better info. Thank you. Thanks to @bill93 (again) as well for his knowledgeable insight. I appreciate it.

"I don’t even know what that statement means..."

Thank you, Chris. My terse statement there was just that this is a 180+ acre undeveloped property where their first effort is placing a detention basin sort of inline with a natural floodway. Poorly designed IMO but apparently permitted with construction begun. The contractor has it located fairly well per "plan" (I also haven't seen any county approved permit plans) but was basing his elevations off what he calls the field map which I believe is data given him by the engineer for an app he showed me on his phone. It may be the ESRI product with pretty aerials and the existing and design topo brought in. In that app, he identified an existing tree at a rough elevation that turns out to be about 6' lower that what I shot. Not surprising as public GIS aerials rarely if ever come within 10' feet of reality in my experience. This put the bottom of his rough grade for the basin 6' higher than needed to accept natural flow and he was wanting confirmation. He has this remote engineer hassling him saying "you didn't get it surveyed?" after literally giving him this "field map" data only to begin. Contractor then asked for CAD and I got the cleaned version of their topo described above - no points, no parcel boundary or site features. When he briefed me and sent the TINs (as dwgs) the first thing I asked him for was a geographic basis for the CAD. He said he probably wouldn't be able to get it. I told him it'd be helpful to know when it was shot as well and with what instruments (I presumed aerial). I should have probably held firm and talked with the engineer myself, but it being 'just a basin' all he said really needed was the elevation difference from the road 300' or 400' down slope (45' vertically) to the rough basin grades. He located it with the field map info and it's proximity to the natural flowline. I knew too that critical elevations would be the the points where the naturalized channel enters the basin.

My attack was creating about 10 points from the TIN outside of the disturbed area to compare vertical and shooting the curving natural floodway thalweg downstream of the project, which is scoured to solid rock about 6-10' wide, for vertical and horizontal. I shot it in SPC and made a single 7' (well 7.254') adjustment horizontally in the field to make it look like a reasonable fit... and checking the natural point at the inlet to the basin, it checked with .3' vertically so I'm sure it'll work as designed.

I decided "actual elevations" are not relevant unless the engineer is hung up on HARN. He may be, so I wanted to make sure I understand that. I'm putting together a narrative that shows the basin will be built functionally as designed, but that not releasing his basis prevents any possibility of setting numbers to a datum that

1) I now see from these posts likely doesn't exist for Hawaii (maybe why I couldn't find any local details on it and with @base9geodesy 's tips I see is not listed with NGS in the NCAT reference)

2) besides the ex topo dwg being + and - .5 to 1½' difference from what was shot, showing that the topo's either old or poor resolution, it still falls within national map accuracies for 2' intervals and

3) with OPUS showing me that their whole TIN is nearly 73' higher than the NAD83(PA11) Ortho Ht, that they likely processed it with a missing geoid. (oddly, their TIN elevation is very close to the ellipsoid height).

Thus, just a basin. I think it'll work. But thanks again to you and all here for the enlightenment and entertainment in this. This'll stick with me.

(by the way, I wish I could work for any of you for a few years. I'm still fairly cheap).

my point is, don't navigate muddy water without knowing what the bottom has in store for you. It could very well sink your ship in the unknown.

@chris-bouffard Man, I wrote a long descriptive message to you RE what "just a basin" meant, ie what it is, what data I asked for and didn't get, how I went about it, how I've documented it, my comfort with it (I think it'll work as designed - well, except that the engineering is wrong IMO, but that's not on me or the contractor), that I found (with all your help) that HARN here is roughly +15cm so inconsequential for the type of work, that the TIN provided looks to be created to the ellipsoid height (+72' over current NAD83 (PA11) datum w/ geoid) so if the engineer comes back at us that I think his work and reluctance to provide critical info could be discredited, and my thanks to you and others here for pointing me toward valuable information that's helped with my confidence in the product.

But somehow it was lost it to the inter-ether when I went to post it. So thank you. I think I ended it with something like "man, I'd love to work for one of you guys for a few years. I'm still fairly cheap".