They want ground distances, No reason to have grid distances for subdivisions, ect. All the mapping and city topo was done on that system so if you measure 1000' feet with a tape it's 1000' between coordinates.?ÿ
We actually looked into that software package, but since we are a largish firm and leadership is unfortunately typical in its grasp of technical skills, no decision was made on the purchase and it just disappeared into the ether.
I ended up developing LDP tools in ESRI Arc using ModelBuilder and NOS NGS Manual 5, plugging in the equations to Python scripts for the various projections and using USGS 3DEP DTMs plus GEOID18 separation grids to get rasters of ellipsoid heights across project areas. I'm sure my tools are a lot more crude than what Dr. Dennis has under the hood.
The Oblique Mercator calcs were particularly aggravating, but paid off when we nailed down a 50-mile corridor on an OM projection with less than 10ppm of distortion. They were going to split the project into three separate jobs with three different CSFs. ?????ÿ
It can be really disappointing to pitch LDPs to folks who should know about the benefits of it (with an LS or GISP), only for them to look back at you blankly and say "But how do we work with state plane?"
Can you please help me understand the difference between 'factor' and 'scale factor'.?ÿ
From Oxford Languages:?ÿ
factor: a number or quantity that when multiplied with another produces a given number or expression."an amount that exceeds it by a factor of 1000 or more"
Both above definitions to me imply that a factor is a ratio.?ÿ
And math-dictionary.com:?ÿ
A?ÿscale factor?ÿis the ratio of sizes of two similar figures.
Thank you!
Melita
Let's start with the scale factor which math-dictionary.com has defined correctly. In the context of map projections, the similar figures are infitesimal distances in any direction from a point on the reference ellipsoid and another one on the map projection.Thus, the distances are differentials and their ratio is the solution of a differential equation. We see just an 8 or 9 significant digit number on Data Sheets, but there's a fair amount of mathematics behind it.?ÿ
If we have the geographic coordinates of two points and map projection coordinates for the same two points, then the average scale factor of the line can be computed by computing the ellipsoid distance from the geographic points, the plane distance from the Pythagorean Theorem, and dividing the plane distance by the ellipsoid distance. The answer will be slightly different from the averaged values of the two individual point scale factors.
It's called a scale "factor" because the product of the scale factor and the ellipsoid distance is the plane distance, an identity relationship.
The most general definition of a factor is: "...any of the numbers multiplied to form a product." https://www.math-dictionary.com/definition-of-factor.html
Thus, we multiply our ratio by ellipsoid distance, forming a product, plane distance, and our ratio is a factor. We can multiply the plane distance by the reciprocal of the scale factor to get the ellipsoid distance as a product.
Factor is used in more specific contexts in mathematics. For example, 2*3*5 = 30 and we say that 2, 3, 5 are the prime factors of 30. They are all prime numbers and they form 30 as a product.
Also, (x + 3) and (x + 5) are factors of x^2 +8x + 15. Even more abstract, sqrt(3) and sqrt(5) are factors of sqrt(15).?ÿ
While not all factors are ratios (irrational numbers can be factors) a ratio can be formed from a factor relationsip. For example, 5 * 3 = 15 and 3 = 15/5. In this case, 3 is analogous to average scale factor, 15 is analogous to plane distance and 5 is analogous to ellipsoid distance.
There. I hope I answered your question, but aren't you glad you never had to sit through one of my classea?
?ÿ
Measuring 1000' with a tape and measuring 1000' between coordinates is a scale factor of 1.0, which can also be along the ground.
You seem to be a truly a pleasant person. You seem to be patient, willing to engage, and I think we're all here to support each other, including Team MightyMoe. However, I suspect that many have excercised great restraint and compassion in attempting to address the various topics covered in this thread.
It appears that you understand many things, but your understanding and ability to communicate the concepts, function, and intricacies of SPC/grid/ground/scalars, etc is absolutely fubar.
Whether that's a "precise" vocabulary thing, or something else, I'm not sure.
I know can be a salty SoB, but your comments cause concern because they indicate you either don't get it, or maybe all that bragging about all those years of surveying are really catching up with you?
My $0.02.
(From a concerned "button pusher".)
No, a project scale factor of 1 will leave you on state plane if state plane is the basis.?ÿ
The Project scale factor the city uses is 1.000235 or the compliment of 0.999765.?ÿ
The state plane coordinates are multiplied by the 1.000235 factor and that's where the mapping and topography for the city and surrounding areas were done.?ÿ
I understand there are some field programs that allow a 1 scale factor with no projection/no datum. I've not used them; all our work has always been done in a projection of some type, SPC, LDP, ect.?ÿ
@mightmoe
I understand what you are saying, but my original comment was about "why would a City System be anything other than scale factor of 1.0?"
If the City System was on SPC, then that is how it should be identified, as SPC.
The phrase City System would seem to indicate that the City implemented their own coordinate system, which may be separate from and/or different than SPC.
A city is usually small enough such that Euclidean (planar; scalar = 1.0) geometry is sufficient, and curved geometry is not necessary.
@mightymoe oh how I wish I could get any pair of custom made white logger boots. ?ÿGeezers they were awesome. I do red wings here on east coast but not the loggers . When I was out west in Colorado surveying I loved the whites.
@rover83 It all boils down to change. A book every person should read ??Who moved my cheese? it??s funny it??s partially accurate. ?ÿBut your statement on job security and dropping the ball is in a lot of places. It is really sad because technology has caught up so the time to do simple math is so fast now that it really is no longer an excuse of being burdensome. I wish I could form the words that are ?ÿin my head to state what needs to happen but does not because of simply ATTITUDE. Because its not a lack of ability or the ability for any surveyor to learn this. I am a dyslexic person and not the smartest pea in the patch. But i do have the ATTITUDE of wanting to learn and do whatever it takes to learn. I have been back in private sector side now for almost 2 years now. And not a darn thing has changed. We still have people that are smart as hell but for some darn reason just blow datums and projections to the side and don??t want to deal with them. I quote all i need is 5000 5000 and i can do anything. I don??t need no grid coordinates. Funny thing but also sad is even engineers with this new datums and projections are going to have to get on board because it helps everyone next to and down the road from your project. It??s coming and i am afraid some are going to have an aneurism when it all eventually becomes mandatory. It all is not hard it all is pretty simple. It all can still be used to retrace any boundary because we can look at the ground measurements. And calculate them no matter what tools and what datums. Job security yes because someone will have to fix the work of those not willing to do it correctly. I have followed this thread as close as one can from the seat of a tractor. I have bit my tung a few times on things but i do my best not to judge as I know very well what??s in my head doesn??t make it to the typing. But you and several others have stated very well what all of this is about. Mathteacher etc. others as well. ?ÿI am to pooped and tired as I literally just ended a long day on a tractor. Tomorrow will be the same as raking and stacking small squares will become the family event. But thank the Lord i get to do it all with them. Keep up the good work you do on here as well as many others like math teacher etc. i apologize if I didn??t mention you as my left my other left and all the m names look the same bouncing across the field on my small tractor. And no spectacles on. I can do alright usually figuring out what??s going on but miss key details and names sometimes.
@mightmoe
I understand what you are saying, but my original comment was about "why would a City System be anything other than scale factor of 1.0?"
If the City System was on SPC, then that is how it should be identified, as SPC.
The phrase City System would seem to indicate that the City implemented their own coordinate system, which may be separate from and/or different than SPC.
A city is usually small enough such that Euclidean (planar; scalar = 1.0) geometry is sufficient, and curved geometry is not necessary.
The city system was set up for a water project, later it was incorporated in a mapping project which was also used for flood plain mapping. It started out in the late 80's to tie in the city intake, pipelines, treatment plant and all the other facilities to deliver water. Then it was updated to include the mapping which was used to continue planning and development for the city and surrounding areas.?ÿ
So it wanders west and south of the city and includes areas that are zoned rural residential. The mapping and photos are used extensively.?ÿ
It's was designed on DOT systems that were used in the area since two of the valleys have new DOT projects and the interstate connects both of them. That meant there were ties to large areas of property along all three highway systems. The late 80's control was run conventionally, by the time the mapping flights were done in 2007 the control had been converted to GPS based NAD83(93) numbers. Distances are multiplied by the Project Adjustment Factor of 1.000235 from State Coordinate System grid distances to get surface distances which are "close" to ground in most areas. At the edges I will see between 10-15PPM. ?ÿ
@mightymoe oh how I wish I could get any pair of custom made white logger boots. ?ÿGeezers they were awesome. I do red wings here on east coast but not the loggers . When I was out west in Colorado surveying I loved the whites.
Once you know your size you can get Whites anywhere. I doubt I'll ever get rid of my pair of work boots, I also have the cowboy and the packer, but I only seem to wear them once in a while. I recently boxed the work boots up and sent them in for a reconstruction. Basically they're lifetime boots.
My last comment on this thread. The Project Adjustment Factor is reciprocal of the Average Combined Factor. There is no need for another term for a quantity that that was appropriately named early in the 20th century. There's also no current need to compute the reciprocal of a factor in order to replace tedious division with easier multiplication. Trimble likely got locked into that in the early days, trying to duplicate hand calculations. Now their success has locked them into it.
There is a place for a Project Adjustment Factor in large projects, though. It's the factor that we multiply project budget dollars by in order to convert them to project cost dollars. It's rarely close to one.
@mightymoe Oh that was prior to the year 2000 when I was living in Colorado and I have slept since then and for the life of me I can??t remember what size they gave me back then. Maybe I will travel west again one day and go get remeasured and such. I had a pair of Olathe boots for riding back then as well. But I heard they moved. Now I just settle for off the shelf mass production stuff. I do love my red wing boots but to have a good pair of whites for certain jobs would be nice. Not as necessary here but nice. Here on east coast it is not as harsh on the boots in the form of rocky and steep areas as much. I left Mississippi in the 90??s and went to Colorado. ?ÿAs a young buck. ?ÿI had a pair of Walmart special cheap caterpillar boots. They cost less than 30$ back then. They lasted literally a day or two up in the Leadville area. I was literally barefoot before the day was done. My crew chief took me to town and said look here you have to buy good boots. I started with a set of danners and such. Good boots as well my Walmart boots the sole literally just dismantled from the boot the not so leather just tore up. I was about as wet behind the ears as they come. Talking about a culture shock for a young lad to move across the USA from mud and swamps to Colorado rockies. I was eager and full of zeal. Was on a job and a 6? aspen was in the way. Me and my bush axe which I still have today. Took the aspen out. And my crew chief told me I was in big trouble. It cost the company money because I had no idea that they were being protected. Coming from MS if something was on line we just cut it down most of the time.
@mightymoe Oh that was prior to the year 2000 when I was living in Colorado and I have slept since then and for the life of me I can??t remember what size they gave me back then. Maybe I will travel west again one day and go get remeasured and such. I had a pair of Olathe boots for riding back then as well. But I heard they moved. Now I just settle for off the shelf mass production stuff. I do love my red wing boots but to have a good pair of whites for certain jobs would be nice. Not as necessary here but nice. Here on east coast it is not as harsh on the boots in the form of rocky and steep areas as much. I left Mississippi in the 90??s and went to Colorado. ?ÿAs a young buck. ?ÿI had a pair of Walmart special cheap caterpillar boots. They cost less than 30$ back then. They lasted literally a day or two up in the Leadville area. I was literally barefoot before the day was done. My crew chief took me to town and said look here you have to buy good boots. I started with a set of danners and such. Good boots as well my Walmart boots the sole literally just dismantled from the boot the not so leather just tore up. I was about as wet behind the ears as they come. Talking about a culture shock for a young lad to move across the USA from mud and swamps to Colorado rockies. I was eager and full of zeal. Was on a job and a 6? aspen was in the way. Me and my bush axe which I still have today. Took the aspen out. And my crew chief told me I was in big trouble. It cost the company money because I had no idea that they were being protected. Coming from MS if something was on line we just cut it down most of the time.
I'll be passing through Leadville Thursday, time for me to play some golf. ????
My last comment on this thread. The Project Adjustment Factor is reciprocal of the Average Combined Factor. There is no need for another term for a quantity that that was appropriately named early in the 20th century. There's also no current need to compute the reciprocal of a factor in order to replace tedious division with easier multiplication. Trimble likely got locked into that in the early days, trying to duplicate hand calculations. Now their success has locked them into it.
There is a place for a Project Adjustment Factor in large projects, though. It's the factor that we multiply project budget dollars by in order to convert them to project cost dollars. It's rarely close to one.
Have a great weekend Math Teacher ????
@mightymoe I bet that place has changed a lot. I did a lot of work on the Henderson and Climax mines as a young surveyor. ?ÿSpeaking of golf which I am no golfer lol. But a logging company had done some work around some golf courses and where on the Henderson 2000 project. They brought us a truck load of 5 gallon bucket??s full of old goof balls. We bought some old drivers from a pawn shop and kept them in the survey trucks. At the end of the day we would find some cliff and just sit up and drive golf balls for fun before heading to the hotel. ?ÿI said once I left home to swap my fishing pole in survey rig for a golf club. ?ÿI always wanted to learn the golf thing but a neighbor told me don??t do it or you will end up divorced and broke. Lol ????