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Board » Technical Support » qtVlm thread

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Viva all.

Since some time I have this issue concerning the use of barriers.

The qT I'm using is the version 5.4-3 Nov 1.2016.

Now the issue (pls see also the attached PDF file).

1 - I've open a Grib file for the West Atlantic.

2 - Created a new barrier in the China Sea.

3 - When I zoom to all the Grib's grid space I get two horizontal lines that come from the China Sea created barrier!?

4 - If I want to make a routing N-S in the Atlantic intersecting the Latitudes of those two horizontal lines, I just can't,

5 - unless I clean that barrier.

I would like to know if:

A - This is a problem?
B - The rest of the qT users have the same issue (assuming it is one)?

Thank you.
Sail Fair.
Attachments
Can you send me your poiReal.dat please (I guess this is already corrected but just to check)

--- Dernière modification par maitai le 2016-11-30 07:58:14 ---
Viva Philippe,

Good morning.

I’ll send you the requested file (“poiReal.dat”) but mind you that, meanwhile, I had to remove the Sea China barrier so I could perform the Atlantic routings. Otherwise it was impossible to do it, unless changing the routing option for “Avoid barriers”, which is not an option if we really need “barriers” to be active.

Even now, that I’m making a routing for the X2X race, the polylines from other barriers are generating outside the actual Grib Grid horizontal barrier lines on other areas of the globe.

Thank you & BH
João
Sail Fair.
Thanks for the report João
That's fixed and will be in the next release, due very soon, probably today.
5.4.4-beta1 out on VW (http://www.virtual-winds.org/forum/index.php?/topic/7575-qtvlm/&do=findComment&comment=271697).

Please take your chance to complain/report/suggest before official release ;)
Hey Phillippe
When I draw a heading, the numbers are so small that I can't read them.
Is there a way to enlarge them?
Confusion when increasing TWS Wind Grib.

Viva Philippe.

Good afternoon.

In the qT tab “Advanced settings” tab included in the “Routing settings” menu, there is an option to increase the Wind speed by a percentage that you specify - pls see also attached PDF file.

Made a first test routing with no increase (100%) in the Wind speed and got the first route (blue path).
After, I’ve made a second test routing the Wind speed increased by 15% (115%) and got a second and different route from the first one (purple path).

But what puzzled me was the info I’ve got from qT before the second routing became the second route:

“This routing has been calculated with an assumption modifying grib data”, (so far so good).

The problem came after when, in the same info window had this:

“The route will not take this scenario into account.
Are you sure you want to convert to route?”!?

Well, the two routings were made from the same start and finish marks, starting exactly at the same time. The only different was a15% increase in the TWS for the second routing.
Anyhow, I’ve got two different routes.

The question.

If, as said in the info window that: “The route will not take this scenario into account.”, how and why do we obtain two different routes?

Does it really takes, or not, the effect on the routing and corresponding route the TWS increase?

Thank you and
a BH.

João/psail
Sail Fair.
Attachments
The what-if mechanism only applies to routings, not routes. So once converted in a route you loose them.

You get 2 differents routes because although the route ignore this setting the routing founds other points, of course. So the 2 routes are different, but they are using the same wind.

There is another way to achieve what you want:

In configuration->grib, you can specify a global correction on wind (TWS). Run a routing with this modification, convert it in a route etc, and then FREEZE the route. Then you can reset this setting (or change it) and do a routing->route again, and compare the routes.

Viva Philippe.

Haha, thank you for this good tip (“TWS correction”).

This was precisely what I needed.

BH

João/psail
Sail Fair.
I've directly downloaded some grib2 files from the NOMADS server which include pressure. One uses PRES variable and the other uses PRMSL. Only the PRES one will render the pressure information. I'd prefer to use the PRMSL version if we can get it to work. I've attached the PRMSL grib file for testing.
Attachments

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