why not just 'field action'?

in my opinion 'terreinactie' means an action in the 'field', among the people, rather than doing things on a more abstract level

Example

As part of a multifaceted national campaign, the Service Employees International Union (SEIU) is launching a new national cable television ad on Wednesday to continue the urgent call for commonsense immigration reform.

The multipronged campaign also includes * grassroots and field actions * , coordinated calls to Congress and a major rally April 10 on Capitol Hill with tens of thousands of participants from across the country. The goal of this intense campaign is to urge lawmakers to pass a bipartisan immigration bill that includes a clear and direct roadmap to citizenship.

http://www.enewspf.com/opinion/commentary/41590-seiu-makes-m...

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Note added at 11 hrs (2013-04-14 03:32:18 GMT)
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Actually 'terreinacties' is Belgian Dutch.
I will give you a few examples:
'field activities' rather than 'field actions', as Louis Vorstermans pointed out, may be better depending on the context

Het geld dat ingezameld wordt zal zo snel mogelijk doorgestort worden naar de terreinacties in Haïti van de verschillende organisaties.

http://www.unicef.be/nl/press-release/haiti-lavi-12-12-verhe...

BIPS komt volledig op kruissnelheid. Dit komt tot uiting door het opzetten en uitvoeren van concrete terreinacties om het project de nodige drijfkracht en bekendheid te geven, zoals bv. de 1000-Soortendag of de edities 2011 en 2011 van de Biodiversidays

http://www.bipsweb.eu/nl/page/12/historiek.aspx

Na een initiële fase waarin wordt begonnen met opleiding en onderzoek, zullen de terreinacties in principe in september worden opgestart in het Centraal station. Zij zullen worden
gecoördineerd door een « referent » en geëvalueerd door een onderzoeker, beiden zijn nog aan te duiden.

http://www.lstb.be/pdf/20100521Verslag.pdf



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Note added at 23 hrs (2013-04-14 14:40:54 GMT)
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It does:

(I made and extended the connection through:
- field equipment
- field work / field worker
I was not aware of any problems regarding how it might sound in English)


Field Action

Field Work is an integral part of the programme of training in social work. It consists of practicing social work under the guidance of trained field instructors in selected social welfare agencies and organizations. It enables the student to see the applicability of theoretical knowledge taught in the classroom to actual situations requiring social work intervention.

http://cswnn.edu.in/academics/field-action.php

Field Action Guide

This field action guide focuses on the first psychosocial assessment to be conducted just after a calamity strikes or just after a major event in an ongoing armed conflict. While it is necessary to update that initial assessment as the emergency situation evolves through the different phases of recovery (briefly outlined in the “phase chart”), this mini book is meant to guide the formation of a team to assess the psychosocial as well as physical needs of children, their families and the communities and then the recommendations the team makes for ensuing support.

http://www.unicef.org/eapro/Field_Action_Guide.pdf

NATIONAL ENVIRONMENT AWARENESS CAMPAIGN

The National Environment Awareness Campaign (NEAC) launched by the Ministry of Environment & Forests, Government of India, during 1986-87 seeks to enhance awareness of the people about various environmental issues with a view to invoke their voluntary participation in the efforts for protection of environment and conservation of natural resources. NGOs, educational and training institutions, professional associations, scientific bodies, community organizations besides a range of other agencies including those of the Government participate in the campaign. These bodies singularly or in partnership with other organizations undertake programmes for creating environment and awareness accompanied by * field action * at the local, regional and national level.

http://moef.nic.in/divisions/ee/guidelines-NEAC.pdf

Outdoor activity would also do, but in line with the 'excited' style of the following text, outdoor action is more dynamic.