DMA endpoint returns impression by DMA for National Airings. These impressions are extrapolated using US census data. 

https://api.ispot.tv/v4/metrics/audience/dma?sort=-audience_impressions_national_linear&filter[airing_type]=N,R&filter[national_only]=1&filter[brand]=brandid is the most basic call. Below is a screenshot of the result. Results are broken out by DMA. 

DMA endpoint also supports some group bys. 

For example, to group by creative, https://api.ispot.tv/v4/metrics/audience/dma?filter[group_by]=C&sort=-audience_impressions_national_linear&filter[airing_type]=N,R&filter[national_only]=1&filter[brand]=brandid

Full list of Group bys below. DMA endpoint alo supports multiple group bys. 

GROUP_BY_INDUSTRY = 'I';

GROUP_BY_PARENT_BRAND = 'P';

GROUP_BY_BRAND = 'B';

GROUP_BY_SPOT = 'A';

GROUP_BY_CREATIVE = 'C';

GROUP_BY_DAY_OF_WEEK = 'W';

GROUP_BY_DATE = 'T';

GROUP_BY_MONTH = 'M';

GROUP_BY_WEEK = 'K';

GROUP_BY_DMA_ID = 'Q';

While the DMA endpoint will only return the DMA impressions for National Airings, the API also contains a local endpoint for local airings for some DMAs. Local endpoint does not return national airings nor impressions (for now)

https://api.ispot.tv/v4/metrics/tv/airings/local

Below are the DMAs where local airings will report on. 

Atlanta

Boston (Manchester)

Charlotte

Chicago

Cleveland-Akron (Canton)

Dallas-Ft. Worth

Denver

Detroit

Houston

Indianapolis

Los Angeles

Miami-Ft. Lauderdale

Minneapolis-St. Paul

Nashville

New York

Orlando-Daytona Bch-Melbrn

Philadelphia

Phoenix (Prescott)

Pittsburgh

Portland Or

Sacramnto-Stkton-Modesto

Salt Lake City

San Francisco-Oak-San Jose

Seattle-Tacoma

St. Louis

Tampa-St. Pete (Sarasota)

Washington DC (Hagrstwn