# [ncl-talk] questions about LambertConformal map projection

Mary Haley haley at ucar.edu
Wed Aug 23 13:55:31 MDT 2017

```One thing that can help determine if you have the parallels correct is by
drawing the lat/lon grid of your data. If the lines are straight then this
is a good sign that the map is projected properly. You can use
gsn_coordinates to draw the lat/lon grid.

See example datagrid_8.ncl at:

http://www.ncl.ucar.edu/Applications/datagrid.shtml#ex8

--Mary

On Mon, Aug 21, 2017 at 2:26 PM, Rick Brownrigg <brownrig at ucar.edu> wrote:

> Hi,
>
> Its going to be difficult without knowing these values exactly. A
> reasonable guess on the central meridian might be the center of the area of
> interest, but again its just a guess. The parallels -- who knows?  However,
> if you just pick values or let defaults apply, the worst that should happen
> is a distorted map. You might play around with values until things look
> aesthetic.
>
> Rick
>
> On Mon, Aug 21, 2017 at 6:09 AM, 李雯雯 <jodie_megan at icloud.com> wrote:
>
>> Hello !
>>       I have a matrix which represents a certain quantity ,each point in
>> the matrix has the corresponding latitude and longitude.The longitude of
>> each column in the matrix is not necessarily equal,the latitude of each
>> line is also not necessarily equal.The distance between any grid is 2
>> kilometers.I know the map projection is LambertConformal,but I do not know
>> the res at mpLambertParallel1F, res at mpLambertParallel2F
>> <res at mpLambertParallel2F>,  res at mpLambertMeridianF .Is there any way to
>> calculate the there values?
>>
>> Cheers
>> Sharon
>>
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