Does Changing Microstation Design Resolution Change Geometry Sizes

Rayford,

Think of MicroStation's design plane as a huge piece of graph paper. What you are doing in the "Advanced Settings" part of the dialog is telling MicroStation the spacing between tic marks in the graph paper. With the settings in your first screen shot, when you draw a 1 Survey Foot line, it takes up 12 tic marks. Now suppose you set the Resolution instead to 12000 per foot - then when you draw a 1 foot line, it takes up 12000 tic marks. MicroStation's windowing tools set a minimum number of tic marks that you can see at a time, that is why you can zoom in closer in the second case than the first.

Accuracy, however, is not changed, because the actual coordinates are stored in double precision floating point. So if you wanted to draw a line that is 13 inches, in the first case it takes up 13.5000 tic marks, where in the second case it takes up 13500.0 tic marks. The accuracy is the same.

Because of the limitation on zooming in, however, I suggest you use 1200 or 12000 rather than 12.

To do the test you are describing correctly, set up the Resolution as 12 and raw a one foot line. It will measure as 12 inches or one foot. Now change the Resolution to 12000, and that same line will now measure as .001 foot.

Barry

Rayford,

Think of MicroStation's design plane as a huge piece of graph paper. What you are doing in the "Advanced Settings" part of the dialog is telling MicroStation the spacing between tic marks in the graph paper. With the settings in your first screen shot, when you draw a 1 Survey Foot line, it takes up 12 tic marks. Now suppose you set the Resolution instead to 12000 per foot - then when you draw a 1 foot line, it takes up 12000 tic marks. MicroStation's windowing tools set a minimum number of tic marks that you can see at a time, that is why you can zoom in closer in the second case than the first.

Accuracy, however, is not changed, because the actual coordinates are stored in double precision floating point. So if you wanted to draw a line that is 13 inches, in the first case it takes up 13.5000 tic marks, where in the second case it takes up 13500.0 tic marks. The accuracy is the same.

Because of the limitation on zooming in, however, I suggest you use 1200 or 12000 rather than 12.

To do the test you are describing correctly, set up the Resolution as 12 and raw a one foot line. It will measure as 12 inches or one foot. Now change the Resolution to 12000, and that same line will now measure as .001 foot.

Barry

Hi Barry,

I have always left the Advanced Settings at their defaults of 10000 per Meter. I change the Master Units to US Survey Feet and US Survey Inches, so my measurements readout in my preferred system. The difference is handled internally by MicroStation and I don't need to worry about making the units match.

Is there any worthwhile benefit to changing the Resolution units from Meter to US Survey Foot so that they match the selected Master Units? 

Thanks,
Ron

Not really. If you were looking at the actual stored coordinates of your graphic elements in MicroStation they might make slightly more sense to you, but you never need to do that. Letting MicroStation do the math works just fine.

Barry,

It appears as if you are saying that, in order to see the objects as close, or as far away, as one would like, those objects are actually drawn larger or smaller, but I may be completely misunderstanding what you have said? In working with other drafting software, I have always thought objects were drawn at a set length and location, and the zoom functions worked similar to a microscope being focused in/out on that object in that location. That object stayed the same length and in that location regardless of how close to or far away I zoomed, and the only way it would measure different is if I used a different set of measuring units to measure it with. An easier question to ask (and answer) might be what would be the proper settings (to achieve proper zooming) for working on large site plans that may require one to zoom in on a bolt head of a small pipe fitting in that same drawing?

Rayford,

It is true that many graphics packages don't have the concept of Resolution like MicroStation has. In AutoCAD, for example, the coordinates that are stored are simply in meters or feet or whatever the numbers you enter mean to you. The reason that MicroStation has the concept of Resolution is historical - at one time MicroStation used an integer coordinate system and selecting that resolution value was very important. We retained that resolution concept in the V8 format, even though coordinates are now stored in double precision floating point, to make it easier to convert back and forth from the previous (V7) format to the V8 format. Any reasonable V7 setting would work fine in V8, and thus users with a seed file from the V7 days could simply use it for their V8 seed file and never worry about it. The reason your situation is a little different than we usually encounter is because using 12 per units of resolution (the tic marks in my graph paper analogy) per foot would not have worked at all in the old format, but it mostly works in the V8 format.

As you have discovered, what doesn't work well when using 12 uors per foot is that MicroStation limits your zooming in such that a minimum number of units of resolution are visible at any time. That limitation is for a complicated technical reason that I can't easily explain, so I won't try.

For new files, I recommend that you set up your seed file's Advanced Resolution to 12000 per Survey Foot (since you are using Alabama Geographic Coordinate Systems that use Survey Foot). That will let you zoom in as far as you will ever need to. You will be able to reference those new files to and from your old files with no problems.

However, if you change the Advanced Settings of existing files (from the 12 per Survey Foot that I think you are using now) to 12000 per Survey Foot, the effect will be to scale everything down by a factor of 1000. You can open the files, put a fence around everything and use the scale command to scale everything up by a factor of 1000 to compensate, but that isn't without some risk.

I hope that helps clear it up, but it is a complicated subject that you usually don't have to worry about.

Barry

Well you'll not get a better explanation than that. Thanks Barry.

On the practical side the most recent Alabama seed files are set to US Survey Foot with a resolution of 1000. Those settings will not work well with items drawn less than roughly 1/64 inch. The zoom will stop at 1/1000 foot or .001 or .012 inches. If you're detailing really, really small stuff you could up the resolution.

So update your seed files if you can. For the existing stuff you might open a clean file, attach the older file. Scale it 1:1 then merge it in. As suggested, let Microstation do the math.

Be careful when dealing with any international foot vs survey foot situations. One example is source files from other programs will not have a proper georeferenced coordinate system, they will say foot but were created using survey foot data. Microstation may interpret foot as international foot.