I do not own a DRTK and did not buy one due to the
Emlid units offering better everything. The
Emlid's GNSS chip is a better unit.
Emlid has free point collection and PPK software.
Emlid offers free Caster service where you can buy two
Emlid units, setup one on a known point (NGS monument or your own) and then send NTRIP corrections to your hearts desire.
Emlid has a full support forum where professionals respond to any inquiry within a day or two and will even help explain other helpful information like coordinate and datums.
Your questions.
1. With the
Emlid units yes you can do RTK and PPK. I think you can with the DRTK (You will have to be able to download the RINEX logs)
Emlid has its own PPK software that is very easy to use and was made for drone mappers. You can easily collect GCPs and Check Points with an
Emlid with its easy to use, free data collection software. The newest
Emlid unit RS3 also has tilt compensation which can help to speed up collection.
2. Trimble, Javid, Topcon etc. are higher end than both the
Emlid and D RTK.
Emlid and D RTK are lower price. Yes the highend Trimble and other can collect GCPs. They tend to have harder to use software that may or may not need another subscription or purchase.
3. This is a question that depends on your project. If your project needs low centimeter accuracy than you will have to be receiving corrections. If you just let it sit and average you will NOT have low centimeter accuracy. If you are going the route of spending big bucks for GNSS gear, do it right and get the most accuracy you can. Any project I do whether it requires low centimeter accuracy or not gets it. That way any time I revisit a site my maps will always overlay each other. and have abosulte accuracy so they can overlay other data such as plans, surveys and such. But your clients needs and project may differ. Nothing looks more unprofessional than having two maps of the same area have a shift to them.
I know that RTK subscriptions are expensive, but you do have options if you cannot afford it.
Option 1
Setup your Base on an NGS monument (Link:
ArcGIS Web Application).
Have the Base send corrections to your rover on site. Mark COntrol Points. Have Base Send corrections to drone. This should be less than 20 km away.
Option 2
Same as Option 1, but Have the Rover make a known Point on site collect this point for at least 10 minutes for safety. Then do it again.. Now You can setup a Base on site to send corrections to the Rover for Control Points or the Drone.
Option 3
Setup a Base on Site a day or two before. Log for 12 hours. Run the Logs either through OPUS (Free) or use
Emlid PPK software. You now have a known point to setup your Base on site. It is better to wait 24 hours when using OPUS so you have the actual satellite tracks instead os estimated. NGS has the free logs from the PPK CORS stations and they are easy to download.
Option 4
A day or two before setup a Base on Site and log. Use Rover to collect GCPs. PPK both the Base's Position and then correct the Rovers collection data with PPK.
Option 5
If you map locally make a known point at your house/office using PPK or OPUS. Setup an
Emlid as a full time Base. Send corrections over NTRIP using Emlids free Caster software. Map away to your hearts desire!
Option 6
Rock RTK has a dirt cheap RTK subscription service. But if you buy a $700 base and set it up on your roof for the Rock RTK network to use, you will have free access to it. I have tested this in my area and it is okay. It is not as accurate as my other RTK service, but is not bad. THeir pricing is around $50 per month.
Option 7
Use Point One RTK subscription. A big problem is that they broadcast NTRIP in WGS 84 which is most likely not what most clients want their data in. You would have to transform both horizontal and vertical.
There are more options, but these shoudl suffice for most use cases.
Be aware of what datum any RTK service is sending corrections in. Most popular ones use NAD83(2011) with ellipsoid elevations. But some do not.
Another tip is collect everything in the same datum. Example: Collect the drone images in NAD83(2011) with ellipsoid, and then collect your Control points in the same. Then use Pix4D or Agisoft to apply the geoid. This helps to prevent any confusion when collecting in geographic coordinates vs projections.